U.S. patent application number 16/715633 was filed with the patent office on 2021-02-04 for frequency generation in a quantum controller.
The applicant listed for this patent is Quantum Machines. Invention is credited to Yonatan Cohen, Nissim Ofek, Itamar Sivan.
Application Number | 20210036692 16/715633 |
Document ID | / |
Family ID | 1000004537047 |
Filed Date | 2021-02-04 |
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United States Patent
Application |
20210036692 |
Kind Code |
A1 |
Cohen; Yonatan ; et
al. |
February 4, 2021 |
Frequency Generation in a Quantum Controller
Abstract
A system comprises time-tracking circuitry and phase parameter
generation circuitry. The time-tracking circuitry is operable to
generate a time-tracking value corresponding to time elapsed since
a reference time. The phase parameter generation circuitry operable
to: receive the time-tracking value; receive a control signal that
conveys a frequency parameter corresponding to a desired frequency
of an oscillating signal; and generate a plurality of phase
parameters used for generation of an oscillating signal, wherein
the generation of the plurality of phase parameters is based on the
time-tracking value and the frequency parameter such that the
oscillating signal maintains phase continuity across changes in the
frequency parameter.
Inventors: |
Cohen; Yonatan; (Tel Aviv,
IL) ; Ofek; Nissim; (Tel Aviv, IL) ; Sivan;
Itamar; (Tel Aviv, IL) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Quantum Machines |
Tel Aviv |
|
IL |
|
|
Family ID: |
1000004537047 |
Appl. No.: |
16/715633 |
Filed: |
December 16, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16527782 |
Jul 31, 2019 |
10560076 |
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16715633 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03K 3/38 20130101; G06N
10/00 20190101 |
International
Class: |
H03K 3/38 20060101
H03K003/38; G06N 10/00 20060101 G06N010/00 |
Claims
1. A system comprising: time-tracking circuitry operable to
generate a time-tracking value corresponding to time elapsed since
a reference time; phase parameter generation circuitry operable to:
receive the time-tracking value; and receive a control signal that
conveys a frequency parameter corresponding to a desired frequency
of an oscillating signal; and generate a plurality of phase
parameters used for generation of the oscillating signal, wherein
the generation of the plurality of phase parameters is based on the
time-tracking value and the frequency parameter such that the
oscillating signal maintains phase continuity across changes in the
frequency parameter.
2. The system of claim 1, wherein the time-tracking circuitry
comprises a register operable to store the time-tracking value and
increment the time-tracking value on each cycle of a clock.
3. The system of claim 1, comprising signal generation circuitry
operable to generate the oscillating signal based on the plurality
of phase parameters.
4. The system of claim 3, wherein the signal generation circuitry
comprises a CORDIC circuit and a plurality of phase rotator
circuits.
5. The system of claim 1, wherein the phase parameter generation
circuitry is operable to alter the plurality of phase parameters
over time to achieve a frequency chirp.
6. The system of claim 1, wherein the phase parameter generation
circuitry is operable to: receive a frequency chirp control signal;
and determine an amount by which to alter the plurality of phase
parameters based on a value of a the frequency chirp control
signal.
7. The system of claim 6, comprising control circuitry operable to
adjust the value of frequency chirp control signal during runtime
based on a feedback signal.
8. The system of claim 1, comprising control circuitry operable to
generate the frequency parameter.
9. The system of claim 8, wherein the control circuitry is operable
to alter the frequency parameter during runtime based on a feedback
signal.
10. The system of claim 1, wherein each of the plurality of phase
parameters has a phase offset relative to others of the phase
parameters.
11. A system comprising: time-tracking circuitry operable to
generate a time-tracking value corresponding to time elapsed since
a reference time; phase parameter generation circuitry operable to:
receive the time-tracking value; and receive a control signal that
conveys a frequency parameter corresponding to a desired frequency
of an oscillating signal; and generate a phase parameter used for
generation of the oscillating signal, wherein the generation of the
phase parameter is based on the time-tracking value and the
frequency parameter such that the oscillating signal maintains
phase continuity across changes in the frequency parameter.
12. The system of claim 11, wherein the time-tracking circuitry
comprises a register operable to store the time-tracking value and
increment the time-tracking value on each cycle of a clock.
13. The system of claim 11, comprising signal generation circuitry
operable to generate the oscillating signal based on the phase
parameter.
14. The system of claim 13, wherein the signal generation circuitry
comprises a CORDIC circuit.
15. The system of claim 11, wherein the phase parameter generation
circuitry is operable to alter the phase parameter over time to
achieve a frequency chirp.
16. The system of claim 11, wherein the phase parameter generation
circuitry is operable to: receive a frequency chirp control signal;
and determine an amount by which to alter the phase parameter based
on a value of a the frequency chirp control signal.
17. The system of claim 16, comprising control circuitry operable
to adjust the value of frequency chirp control signal during
runtime based on a feedback signal.
18. The system of claim 11, comprising control circuitry operable
to generate the frequency parameter.
19. The system of claim 18, wherein the control circuitry is
operable to alter the frequency parameter during runtime based on a
feedback signal.
20. The system of claim 11, wherein the changes in the frequency
parameter comprises changing the frequency parameter from a first
value to a second value and then back to the first value.
Description
PRIORITY CLAIM
[0001] This application is a continuation of Ser. No. 16/527,782
filed on Jul. 31, 2019, the entirety of which is hereby
incorporated herein by reference.
BACKGROUND
[0002] Limitations and disadvantages of conventional approaches to
frequency generation in quantum computer control systems will
become apparent to one of skill in the art, through comparison of
such approaches with some aspects of the present method and system
set forth in the remainder of this disclosure with reference to the
drawings.
BRIEF SUMMARY
[0003] Methods and systems are provided for frequency generation in
a quantum controller, substantially as illustrated by and/or
described in connection with at least one of the figures, as set
forth more completely in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIGS. 1A and 1B compare some aspects of classical (binary)
computing and quantum computing.
[0005] FIG. 2 shows an example quantum computing system.
[0006] FIG. 3A shows an example quantum controller architecture in
accordance with various example implementations of this
disclosure.
[0007] FIG. 3B shows an example implementation of the quantum
controller circuitry of FIG. 3A.
[0008] FIG. 4 shows an example implementation of the puller of FIG.
3B.
[0009] FIG. 5 shows an example implementation of the pulse
operations manager and pulse operations circuitry of FIG. 3B.
[0010] FIG. 6A shows frequency generation circuitry of the quantum
controller of FIG. 3B.
[0011] FIG. 6B shows example components of the control signal
IF.sub.I of FIG. 6A.
[0012] FIGS. 7A and 7B illustrate phase continuity across frequency
hops in the frequency generation circuitry of FIGS. 6A and 6B.
[0013] FIGS. 8A and 8B illustrate upconversion of a quantum control
pulse in an example implementation of this disclosure.
[0014] FIG. 9 shows an example configuration of the frequency
generation circuitry of FIGS. 6A and 6B to support higher output
sample rates.
[0015] FIGS. 10A and 10B illustrate upconversion of a quantum
control pulse in an example implementation of this disclosure.
[0016] FIG. 11 shows another example configuration of the frequency
generation circuitry of FIGS. 6A and 6B to support higher output
sample rates.
[0017] FIG. 12A shows an example frequency generation circuitry
operable to generate chirps.
[0018] FIG. 12B shows example components of the control signal
IF.sub.I of FIG. 12A.
DETAILED DESCRIPTION
[0019] Classical computers operate by storing information in the
form of binary digits ("bits") and processing those bits via binary
logic gates. At any given time, each bit takes on only one of two
discrete values: 0 (or "off") and 1 (or "on"). The logical
operations performed by the binary logic gates are defined by
Boolean algebra and circuit behavior is governed by classical
physics. In a modern classical system, the circuits for storing the
bits and realizing the logical operations are usually made from
electrical wires that can carry two different voltages,
representing the 0 and 1 of the bit, and transistor-based logic
gates that perform the Boolean logic operations.
[0020] Shown in FIG. 1A is a simple example of a classical computer
configured to a bit 102 and apply a single logic operation 104 to
the bit 102. At time t0 the bit 102 is in a first state, at time t1
the logic operation 104 is applied to the bit 102, and at time t2
the bit 102 is in a second state determined by the state at time t0
and the logic operation. So, for example, the bit 102 may typically
be stored as a voltage (e.g., 1 Vdc for a "1 " or 0 Vdc for a "0 ")
which is applied to an input of the logic operation 104 (comprised
of one or more transistors). The output of the logic gate is then
either 1 Vdc or 0 Vdc, depending on the logic operation
performed.
[0021] Obviously, a classical computer with a single bit and single
logic gate is of limited use, which is why modern classical
computers with even modest computation power contain billions of
bits and transistors. That is to say, classical computers that can
solve increasingly complex problems inevitably require increasingly
large numbers of bits and transistors and/or increasingly long
amounts of time for carrying out the algorithms. There are,
however, some problems which would require an infeasibly large
number of transistors and/or infeasibly long amount of time to
arrive at a solution. Such problems are referred to as
intractable.
[0022] Quantum computers operate by storing information in the form
of quantum bits ("qubits") and processing those qubits via quantum
gates. Unlike a bit which can only be in one state (either 0 or 1 )
at any given time, a qubit can be in a superposition of the two
states at the same time. More precisely, a quantum bit is a system
whose state lives in a two dimensional Hilbert space and is
therefore described as a linear combination
.alpha.|0>+.beta.|1>, where |0 and |1 are two basis states,
and .alpha. and .beta. are complex numbers, usually called
probability amplitudes, which satisfy
|.alpha.|.sup.2+|.beta.|.sup.2=1. Using this notation, when the
qubit is measured, it will be 0 with probability |.alpha.|.sup.2
and will be 1 with probability |.beta.|.sup.2. |0 and |1 can also
be represented by two-dimensional basis vectors
[ 1 0 ] ##EQU00001##
and
[ 0 1 ] , ##EQU00002##
respectively, and then the qubit state is represented by
[ .alpha. .beta. ] . ##EQU00003##
The operations performed by the quantum gates are defined by linear
algebra over Hilbert space and circuit behavior is governed by
quantum physics. This extra richness in the mathematical behavior
of qubits and the operations on them, enables quantum computers to
solve some problems much faster than classical computers (in fact
some problems that are intractable for classical computers may
become trivial for quantum computers).
[0023] Shown in FIG. 1B is a simple example of a quantum computer
configured to store a qubit 122 and apply a single quantum gate
operation 124 to the qubit 122. At time t0 the qubit 122 is
described by .alpha..sub.1|0+.beta..sub.1|1, at time t1 the logic
operation 104 is applied to the qubit 122, and at time t2 the
qubits 122 is described by .alpha..sub.2|0+.beta..sub.2|1.
[0024] Unlike a classical bit, a qubit cannot be stored as a single
voltage value on a wire. Instead, a qubit is physically realized
using a two-level quantum mechanical system. Many physical
implementations of qubits have been proposed and developed over the
years with some being more promising than others. Some examples of
leading qubits implementations include superconducting circuits,
spin qubits, and trapped ions.
[0025] It is the job of the quantum controller to generate the
precise series of external signals, usually pulses of
electromagnetic waves and pulses of base band voltage, to perform
the desired logic operations (and thus carry out the desired
quantum algorithm). Example implementations of a quantum controller
are described in further detail below.
[0026] FIG. 2 shows an example quantum computing system. The system
comprises a quantum programming subsystem 202, a quantum controller
210, and a quantum processor 218.
[0027] The quantum programming subsystem 202 comprises circuitry
operable to generate a quantum algorithm description 206 which the
quantum controller 210 can execute to carry out the quantum
algorithm on the quantum processor 218 (i.e., generate the
necessary outbound quantum pulse(s) 213) with little or no human
intervention during runtime of the algorithm. In an example
implementation, the quantum programming system 202 is a personal
computer having installed on it a quantum controller software
development kit (SDK) that enables a user to generate the quantum
algorithm description 206 using a programming language. In an
example implementation, the programming language may be a low-level
language which has little or no abstraction from the instruction
set used by the specific hardware of the quantum controller 210.
Such instructions may be converted to machine code of the quantum
controller 210 without need of a compiler or interpreter. In an
example implementation, the programming language may be a
high-level language which is much more abstracted from the
particular hardware of the quantum controller 210. Such
instructions may be compiled into machine code before they can be
run on the quantum controller 210. In an example implementation the
description 206 may be a machine code description of the quantum
algorithm. In an example implementation, the description 206 may be
a high-level description which the quantum controller 210 may
itself compile into machine code. In an example implementation, the
description 206 may be a high-level description which the quantum
controller 210 may interpret into machine code during runtime. In
an example implementation, an operating system or other software
layer may run on the quantum controller 210 and the quantum
algorithm description 206 may be software instructions that make
use of an application programming interface (API) of the software
running on the quantum controller 210.
[0028] The quantum programming subsystem 202 is coupled to the
quantum controller 210 via interconnect 204 which may, for example,
utilize universal serial bus (USB), peripheral component
interconnect (PCIe) bus, wired or wireless Ethernet, or any other
suitable communication protocol.
[0029] The quantum controller 210 omprises circuitry operable to
load the quantum algorithm description 206 and then perform the
quantum algorithm as per the quantum algorithm description 206. In
an example implementation, quantum algorithm description 206 is
machine code (i.e., series of binary vectors that represent
instructions that the quantum controller's hardware can interpret
and execute directly) which is loaded into the quantum controller
210 to generate the necessary outbound quantum control pulse(s) 213
that correspond to the desired operations to be performed on the
quantum processor 218 (e.g., sent to qubit(s) for manipulating a
state of the qubit(s) or to readout resonator(s) for reading the
state of the qubit(s), etc.). Depending on the quantum algorithm to
be performed, outbound pulse(s) 213 for carrying out the algorithm
may be predetermined at design time and/or may need to be
determined during runtime. The runtime determination of the pulses
may comprise performance of classical calculations and processing
in the quantum controller 210 and/or the quantum programing
subsystem 202 during runtime of the algorithm (e.g., runtime
analysis of inbound pulses 215 received from the quantum processor
218).
[0030] Upon completion of a quantum algorithm and/or during a
runtime of a quantum algorithm by the quantum controller 210, the
quantum controller 210 may output data/results 208 to the quantum
programming subsystem 202. In an example implementation these
results may be used to generate a new quantum algorithm description
206 for a subsequent run of the quantum algorithm and/or update the
quantum algorithm description during runtime.
[0031] The quantum controller 210 is coupled to the quantum
processor 218 via interconnect 212 which may comprise, for example,
one or more conductors and/or optical fibers.
[0032] The quantum processor 218 comprises K (an integer) quantum
elements 122, which includes qubits (which could be of any type
such as superconducting, spin qubits, ion trapped, etc.), and,
where applicable, any other element(s) for processing quantum
information, storing quantum information (e.g. storage resonator),
and/or coupling the outbound quantum control pulses 213 and inbound
quantum control pulses 215 between interconnect 212 and the quantum
element(s) 122 (e.g., readout resonator(s)). In an example
implementation in which the quantum processor comprises readout
resonators (or other readout circuitry) K may be equal the total
number of qubits plus the number of readout circuits. That is, if
each of Q (an integer) qubits of the quantum processor 218 is
associated with a dedicated readout circuit, then K may be equal to
2Q. For ease of description, the remainder of this disclosure will
assume such an implementation, but it need not be the case in all
implementations. Other elements of the quantum processor 218 may
include, for example, flux lines (electronic lines for carrying
current), gate electrodes (electrodes for voltage gating),
current/voltage lines, amplifiers, classical logic circuits
residing on-chip in the quantum processor 218, and/or the like.
[0033] FIG. 3A shows an example quantum controller architecture in
accordance with various example implementations of this disclosure.
The quantum controller 210 comprises L (an integer 1) pulser
circuits 302.sub.0-302.sub.L-1 and shared circuitry 310.
[0034] In the example implementation shown, each pulser circuit
302.sub.I (I an integer between 0 and L-1) comprises circuitry for
exchanging information over signal paths 304.sub.I, 306.sub.I, and
308.sub.I, where the signal path 308.sub.I carries outbound pulses
(e.g., 213 of FIG. 2) generated by the pulser circuit 302.sub.I
(which may be, for example, control pulses sent to the quantum
processor 128 to manipulate one or more properties of one or more
quantum elements e.g., manipulate a state of one or more qubits,
manipulate a frequency of a qubit using flux biasing, etc., and/or
readout a state of one or more quantum elements), the signal path
306.sub.I carries inbound quantum element readout pulses (e.g., 215
of FIG. 2) to be processed by the pulser circuit 302.sub.I, and
signal path 304.sub.I carries control information. Each signal path
may comprise one or more conductors, optical channels, and/or
wireless channels.
[0035] Each pulser circuit 302.sub.I comprises circuitry operable
to generate outbound pulses on signal path 308.sub.I according to
quantum control operations to be performed on the quantum processor
218. This involves very precisely controlling characteristics such
as phase, frequency, amplitude, and timing of the outbound pulses.
The characteristics of an outbound pulse generated at any
particular time may be determined, at least in part, on inbound
pulses received from the quantum processor 218 (via shared
circuitry 310 and signal path 306.sub.I) at a prior time. In an
example implementation, the time required to close the feedback
loop (i.e., time from receiving a first pulse on one or more of
paths 315.sub.1-315.sub.L (e.g., at an analog to digital converter
of the path) to sending a second pulse on one or more of paths
313.sub.0-313.sub.L-1 (e.g., at an output of a digital-to-analog
converter of the path), where the second pulse is based on the
first pulse) is significantly less than the coherence time of the
qubits of the quantum processor 218. For example, the time to close
the feedback loop may be on the order of 100 nanoseconds. It should
be noted that each signal path in FIG. 3A may in practice be a set
of signal paths for supporting generation of multi-pulse sets
(e.g., two signal paths for two-pulse pairs, three signal paths for
three-pulse sets, and so on).
[0036] In the example implementation shown, the shared circuitry
310 comprises circuitry for exchanging information with the pulser
circuits 302.sub.0-302.sub.L-1 over signal paths
304.sub.0-304.sub.L-1, 306.sub.0-306.sub.L-1, and
308.sub.0-308.sub.L-1, where each signal path 308.sub.I carries
outbound pulses generated by the pulser circuit 302.sub.I, each
signal path 306.sub.I carries inbound pulses to be processed by
pulser circuit 302.sub.I, and each signal path 304.sub.I carries
control information such as flag/status signals, data read from
memory, data to be stored in memory, data streamed to/from the
quantum programming subsystem 202, and data to be exchanged between
two or more pulsers 302.sub.0-302.sub.L. Similarly, in the example
shown the shared circuitry 310 comprises circuitry for exchanging
information with the quantum processor 218 over signal paths
315.sub.0-315.sub.M-1 and 313.sub.1-313.sub.K-1, where each signal
path 315.sub.m (m an integer between 0 and M-1) carries inbound
pulses from the quantum processor 218, and each signal path
313.sub.k (k an integer between 0 and K-1) carries outbound pulses
to the quantum processor 218. Additionally, in the example shown
the shared circuitry 310 comprises circuitry for exchanging
information with the quantum programming subsystem over signal path
311. The shared circuitry 310 may be: integrated with the quantum
controller (e.g., on the same field programmable gate array or
application specific integrated circuitry or printed circuit
board); external to the quantum controller (e.g., on a separate
FPGA, ASIC, or PCB connected to the quantum controller via one or
more cables, backplanes, in other devices connected to the quantum
processor 218, etc.); or partially integrated with the quantum
controller and partially external to the quantum controller.
[0037] In various implementations, M may be less than, equal to, or
greater than L, K may be less than, equal to, or greater than L,
and M may be less than, equal to, or greater than K. For example,
the nature of some quantum algorithms is such that not all K
quantum elements need to be driven at the same time. For such
algorithms, L may be less than K and one or more of the L pulsers
302.sub.I may be shared among multiple of the K quantum elements
circuits. That is, any pulser 302.sub.I may generate pulses for
different quantum elements at different times. This ability of a
pulser 302.sub.I to generate pulses for different quantum elements
at different times can reduce the number of pulsers
302.sub.0-302.sub.L-1 (i.e., reduce L) required to support a given
number of quantum elements (thus saving significant resources,
cost, size, overhead when scaling to larger numbers of qubits,
etc.).
[0038] The ability of a pulser 302.sub.I to generate pulses for
different quantum elements at different times also enables reduced
latency. As just one example, assume a quantum algorithm which
needs to send a pulse to quantum element 122.sub.0 at time T1, but
whether the pulse is to be of a first type or second type (e.g.,
either an X pulse or a Hadamard pulse) cannot be determined until
after processing an inbound readout pulse at time T1-DT (i.e., DT
time intervals before the pulse is to be output). If there were a
fixed assignment of pullers 302.sub.0-302.sub.L-1 to quantum
elements of the quantum processor 218 (i.e., if 302.sub.0 could
only send pulses to quantum element 122.sub.0, and 302.sub.1 could
only send pulses to quantum element 122.sub.1, and so on), then
pulser 302.sub.0 might not be able to start generating the pulse
until it determined what the type was to be. In the depicted
example implementation, on the other hand, pulser 302.sub.0 can
start generating the first type pulse and pulser 302.sub.1 can
start generating the second type pulse and then either of the two
pulses can be released as soon as the necessary type is determined.
Thus, if the time to generate the pulse is T.sub.lat, in this
example the example quantum controller 210 may reduce latency of
outputting the pulse by T.sub.lat.
[0039] The shared circuitry 310 is thus operable to receive pulses
via any one or more of the signals paths 308.sub.0-308.sub.L-1
and/or 315.sub.0-315.sub.M-1, process the received pulses as
necessary for carrying out a quantum algorithm, and then output the
resulting processed pulses via any one or more of the signal paths
306.sub.0-306.sub.L-1 and/or 313.sub.0-313.sub.K-1. The processing
of the pulses may take place in the digital domain and/or the
analog domain. The processing may comprise, for example: frequency
translation/modulation, phase translation/modulation, frequency
and/or time division multiplexing, time and/or frequency division
demultiplexing, amplification, attenuation, filtering in the
frequency domain and/or time domain, time-to-frequency-domain or
frequency-to-time-domain conversion, upsampling, downsampling,
and/or any other signal processing operation. At any given time,
the decision as to from which signal path(s) to receive one or more
pulse(s), and the decision as to onto which signal path(s) to
output the pulse(s) may be: predetermined (at least in part) in the
quantum algorithm description; and/or dynamically determined (at
least in part) during runtime of the quantum algorithm based on
classical programs/computations performed during runtime, which may
involve processing of inbound pulses. As an example of
predetermined pulse generation and routing, a quantum algorithm
description may simply specify that a particular pulse with
predetermined characteristics is to be sent to signal path
313.sub.1 at a predetermined time. As an example of dynamic pulse
determination and routing, a quantum algorithm description may
specify that an inbound readout pulse at time T-DT should be
analyzed and its characteristics (e.g., phase, frequency, and/or
amplitude) used to determine, for example, whether at time T pulser
302.sub.I should output a pulse to a first quantum element or to a
second quantum element or to determine, for example, whether at
time T pulser 302.sub.I should output a first pulse to a first
quantum element or a second pulse to the first quantum element. In
various implementations of the quantum controller 210, the shared
circuitry 310 may perform various other functions instead of and/or
in addition to those described above. In general, the shared
circuitry 310 may perform functions that are desired to be
performed outside of the individual pulser circuits
302.sub.0-302.sub.L-1. For example, a function may be desirable to
implement in the shared circuitry 310 where the same function is
needed by a number of pulser circuits from 302.sub.0-302.sub.L-1
and thus may be shared among these pulser circuits instead of
redundantly being implemented inside each pulser circuit. As
another example, a function may be desirable to implement in the
shared circuitry 310 where the function is not needed by all pulser
circuits 302.sub.0-302.sub.L-1 at the same time and/or on the same
frequency and thus fewer than L circuits for implementing the
function may be shared among the L pulser circuits
302.sub.0-302.sub.L-1 through time and/or frequency division
multiplexing. As another example, a function may be desirable to
implement in the shared circuitry 310 where the function involves
making decisions based on inputs, outputs, and/or state of multiple
of the L pulser circuits 302.sub.0-302.sub.L-1, or other circuits.
Utilizing a centralized coordinator/decision maker in the shared
circuitry 310 may have the benefit(s) of: (1) reducing pinout and
complexity of the pulser circuits 302.sub.0-302.sub.L-1; and/or (2)
reducing decision-making latency. Nevertheless, in some
implementations, decisions affecting multiple pulser circuits
302.sub.0-302.sub.L-1 may be made by one or more of the pulser
circuits 302.sub.0-302.sub.L-1 where the information necessary for
making the decision can be communicated among pulser circuits
within a suitable time frame (e.g., still allowing the feedback
loop to be closed within the qubit coherence time) over a tolerable
number of pins/traces.
[0040] FIG. 3B shows an example implementation of the quantum
controller of FIG. 2. The example quantum controller shown
comprises pulsers 302.sub.1-302.sub.L-1, receive analog frontend
350, input manager 352, digital manager 354, pulse operations
manager 356, pulse operations 358, output manager 360, transmit
analog frontend 362, data exchange 364, synchronization manager
366, and input/output ("I/O") manager 368. Circuitry depicted in
FIG. 3B other than pulser circuits 302.sub.0-302.sub.L-1
corresponds to an example implementation of the shared circuitry
310 of FIG. 3A.
[0041] The receive analog frontend 350 comprises circuitry operable
to concurrently process up to M (an integer .gtoreq.1) analog
inbound signals (RP'.sub.0-RP'.sub.M-1) received via signal paths
315.sub.0-315 .sub.M-1 to generate up to M concurrent inbound
signals (RP.sub.0-RP.sub.M-1) to be output to input manager 352 via
one or more signal paths. Although there is shown to be M signals
RP and M signals RP', this need not be the case. Such processing
may comprise, for example, analog-to-digital conversion, filtering,
upconversion, downconversion, amplification, attenuation, time
division multiplexing/demultiplexing, frequency division
multiplexing/demultiplexing, and/or the like. In various
implementations, M may be less than, equal to, or greater than L
and M may be less than, equal to, or greater than K.
[0042] The input manager 352 comprises circuitry operable to route
any one or more of signals (RP.sub.0-RP.sub.M-1) to any one or more
of pulsers 302.sub.0-302.sub.L-1 (as signal(s) AI.sub.0-AI.sub.L-1)
and/or to other circuits (e.g. as signal io_mgr to I/O manager
368). In an example implementation, the input manager 352 comprises
one or more switch networks, multiplexers, and/or the like for
dynamically reconfiguring which signals RP.sub.0-RP.sub.M-1 are
routed to which pulsers 302.sub.0-302.sub.L-1. This may enable time
division multiplexing multiple of the signals RP.sub.0-RP.sub.M-1
onto a single signal AI.sub.I and/or time division demultiplexing
components (e.g., time slices) of a signal RP.sub.m onto multiple
of the signals AI.sub.0-AI.sub.L-1. In an example implementation,
the input manager 352 comprises one or more mixers and/or filters
for frequency division multiplexing multiple of the signals
RP.sub.0-RP.sub.M-1 onto a single signal AI.sub.I and/or frequency
division demultiplexing components (e.g., frequency bands) of a
signal RP.sub.m onto multiple of the signals AI.sub.0-AI.sub.L-1.
The signal routing and multiplexing/demultiplexing functions
performed by the input manager 352 enables: a particular pulser
302.sub.I to process different inbound pulses from different
quantum elements at different times; a particular pulser 302.sub.I
to process different inbound pulses from different quantum elements
at the same time; and multiple of the pulsers 302.sub.0-302.sub.L-1
to processes the same inbound pulse at the same time. In the
example implementation shown, routing of the signals
RP.sub.0-RP.sub.M-1 among the inputs of the pulsers
302.sub.0-302.sub.L-1 is controlled by digital control signals
in_slct.sub.0-in_slct.sub.L-1 from the pulsers
302.sub.0-302.sub.L-1. In another implementation, the input manager
may be operable to autonomously determine the appropriate routing
(e.g., where the quantum algorithm description includes
instructions to be loaded into memory of, and executed by, the
input manager 352). In the example implementation, the input
manager 352 is operable to rout input signals RP.sub.0-RP.sub.M-1
to the I/O manager 368 (as signal(s) io_mgr), to be sent to the
quantum programing subsystem 202. This routing may, for example, be
controlled by signals from the digital manager 354. In an example
implementation, for each input signal RP.sub.m there is a digital
signal, stream.sub.m, from the digital manager 354 to the input
manager 352 that controls whether RP.sub.m will be sent from the
input manager 352 to the I/O manager 368 and from there to the
quantum programing subsystem 202.
[0043] Each of the pulsers 302.sub.0-302.sub.L-1 is as described
above with reference to FIG. 3A. In the example implementation
shown, each pulser 302.sub.I is operable to generate raw outbound
pulses CP'.sub.I ("raw" is used simply to denote that the pulse has
not yet been processed by pulse operations circuitry 358) and
digital control signals in_slct.sub.I, D_port.sub.I, D.sub.I,
out_slct.sub.I, ops_ctrl.sub.I, ops_slct.sub.I, IF.sub.I, F.sub.I,
and dmod_sclt.sub.I for carrying out quantum algorithms on the
quantum processor 218, and results.sub.I for carrying intermediate
and/or final results generated by the pulser 302.sub.I to the
quantum programming subsystem 202. One or more of the pulsers
302.sub.0-302.sub.L-1 may receive and/or generate additional
signals which are not shown in FIG. 3A for clarity of illustration.
The raw outbound pulses CP'.sub.0-CP'.sub.L-1 are conveyed via
signal paths 308.sub.0-308.sub.L-1 and the digital control signals
are conveyed via signal paths 304.sub.0-304.sub.L-1. Each of the
pulsers 302.sub.I is operable to receive inbound pulse signal
AI.sub.I and signal f_dmod.sub.I. Pulser 302.sub.I may process the
inbound signal AI.sub.I to determine the state of certain quantum
element(s) in the quantum processor 218 and use this state
information for making decisions such as, for example, which raw
outbound pulse CP'.sub.I to generate next, when to generate it, and
what control signals to generate to affect the characteristics of
that raw outbound pulse appropriately. Pulser 302.sub.I may use the
signal f_dmod.sub.I for determining how to process inbound pulse
signal AI.sub.I. As an example, when pulser 302.sub.1 needs to
process an inbound signal AI.sub.1 from quantum element 122.sub.3,
it can send a dmod_sclt.sub.1 signal that directs pulse operations
manager 356 to send, on f_dmod.sub.1, settings to be used for
demodulation of an inbound signal AI.sub.1 from quantum element
122.sub.3 (e.g., the pulse operations manager 356 may send the
value cos(.omega..sub.3*TS*T.sub.clk1+.PHI..sub.3), where w.sub.3
is the frequency of quantum element 122.sub.3, TS is amount of time
passed since the reference point, for instance the time at which
quantum algorithm started running, and .PHI..sub.3 is the phase of
the total frame rotation of quantum element 122.sub.3, i.e. the
accumulated phase of all frame rotations since the reference
point).
[0044] The pulse operations circuitry 358 is operable to process
the raw outbound pulses CP'.sub.0-CP'.sub.L-1 to generate
corresponding output outbound pulses CP.sub.0-CP.sub.L-1. This may
comprise, for example, manipulating the amplitude, phase, and/or
frequency of the raw pulse CP'.sub.I. The pulse operations
circuitry 358 receives raw outbound pulses CP'.sub.0-CP'.sub.L-1
from pulsers 302.sub.0-302.sub.L-1, control signals
ops_cnfg.sub.0-ops_cnfg.sub.L-1 from pulse operations manager 356,
and ops_ctrl.sub.0-ops_ctrl.sub.L-1 from pulsers
302.sub.0-302.sub.L-1.
[0045] The control signal ops_cnfg.sub.I configures, at least in
part, the pulse operations circuitry 358 such that each raw
outbound pulse CP'.sub.I that passes through the pulse operations
circuitry 358 has performed on it one or more operation(s) tailored
for that particular pulse. To illustrate, denoting a raw outbound
pulse from pulser 302.sub.3 at time T1 as CP'.sub.3,T1, then, at
time T1 (or sometime before T1 to allow for latency, circuit setup,
etc.), the digital control signal ops_cnfg.sub.3 (denoted
ops_cnfg.sub.3,T1 for purposes of this example) provides the
information (e.g., in the form of one or more matrix, as described
below) as to what specific operations are to be performed on pulse
CP'.sub.3,T1. Similarly, ops_cnfg.sub.4,T1 provides the information
as to what specific operations are to be performed on pulse
CP'.sub.4,T1, and ops_cnfg.sub.3,T2 provides the information as to
what specific operations are to be performed on pulse
CP'.sub.4,T1.
[0046] The control signal ops_ctrl.sub.I provides another way for
the pulser 302.sub.I to configure how any particular pulse is
processed in the pulse operations circuitry 358. This may enable
the pulser 302.sub.I to, for example, provide information to the
pulse operation circuitry 358 that does not need to pass through
the pulse operation manager 356. For example, the pulser 302.sub.I
may send matrix values calculated in real-time by the pulser
302.sub.I to be used by the pulse operation circuitry 358 to modify
pulse CP'.sub.I. These matrix values arrive to the pulse operation
circuitry 358 directly from the pulser 302.sub.I and do not need to
be sent to the pulse operation manager first. Another example may
be that the pulser 302.sub.I provides information to the pulse
operation circuitry 358 to affect the operations themselves (e.g.
the signal ops_ctrl.sub.I can choose among several different
mathematical operations that can be performed on the pulse).
[0047] The pulse operations manager 356 comprises circuitry
operable to configure the pulse operations circuitry 358 such that
the pulse operations applied to each raw outbound pulse CP'.sub.I
are tailored to that particular raw outbound pulse. To illustrate,
denoting a first raw outbound pulse to be output during a first
time interval T1 as CP'.sub.I,T1, and a second raw outbound pulse
to be output during a second time interval T 2 as CP'.sub.I,T2,
then pulse operations circuitry 358 is operable to perform a first
one or more operations on CP'.sub.I,T1 and a second one or more
operations on CP'.sub.1,T2. The first one or more operations may be
determined, at least in part, based on to which quantum element the
pulse CP.sub.1,T1 is to be sent, and the second one or more
operations may be determined, at least in part, based on to which
quantum element the pulse CP.sub.1,T2 is to be sent. The
determination of the first one or more operations and second one or
more operations may be performed dynamically during runtime.
[0048] The transmit analog frontend 362 comprises circuitry
operable to concurrently process up to K digital signals DO.sub.k
to generate up to K concurrent analog signals AO.sub.k to be output
to the quantum processor 218. Such processing may comprise, for
example, digital-to-analog conversion, filtering, upconversion,
downconversion, amplification, attenuation, time division
multiplexing/demultiplexing, frequency division
multiplexing/demultiplexing and/or the like. In an example
implementation, each of the one or more of signal paths
313.sub.0-313.sub.K-1 (FIG. 3A) represents a respective portion of
Tx analog frontend circuit 362 as well as a respective portion of
interconnect 212 (FIG. 2) between the Tx analog frontend circuit
362 and the quantum processor 218. Although there is one-to-one
correspondence between the number of DO signals and the number of
AO signals in the example implementation described here, such does
not need to be the case. In another example implementation, the
analog frontend 362 is operable to map more (or fewer) signals DO
to fewer (or more) signals AO. In an example implementation the
transmit analog frontend 362 is operable to process digital signals
DO.sub.0-DO.sub.K-1 as K independent outbound pulses, as K/2
two-pulse pairs, or process some of signals DO.sub.0-DO.sub.K-1 as
independent outbound pulses and some signals DO.sub.0-DO.sub.K-1 as
two-pulse pairs (at different times and/or concurrently.
[0049] The output manager 360 comprises circuitry operable to route
any one or more of signals CP.sub.0-CP.sub.L-1 to any one or more
of signal paths 313.sub.0-313.sub.K-1. As just one possible
example, signal path 313.sub.0 may comprise a first path through
the analog frontend 362 (e.g., a first mixer and DAC) that outputs
AO.sub.0 and traces/wires of interconnect 212 that carry signal
AO.sub.0; signal path 313.sub.1 may comprise a second path through
the analog frontend 362 (e.g., a second mixer and DAC) that outputs
AO.sub.1 and traces/wires of interconnect 212 that carry signal
AO.sub.1, and so on. In an example implementation, the output
manager 360 comprises one or more switch networks, multiplexers,
and/or the like for dynamically reconfiguring which one or more
signals CP.sub.0-CP.sub.L-1 are routed to which signal paths
313.sub.0-313.sub.K-1. This may enable time division multiplexing
multiple of the signals CP.sub.0-CP.sub.L-1 onto a single signal
path 313.sub.k and/or time division demultiplexing components
(e.g., time slices) of a signal CP.sub.m onto multiple of the
signal paths 313.sub.0-313.sub.K-1. In an example implementation,
the output manager 360 comprises one or more mixers and/or filters
for frequency division multiplexing multiple of the signals
CP.sub.0-CP.sub.M-1 onto a single signal path 313.sub.k and/or
frequency division demultiplexing components (e.g., frequency
bands) of a signal CP.sub.m onto multiple of the signal paths
313.sub.0-313.sub.K-1. The signal routing and
multiplexing/demultiplexing functions performed by the output
manager 360 enables: routing outbound pulses from a particular
pulser 302.sub.I to different ones of the signal paths
313.sub.0-313.sub.K-1 at different times; routing outbound pulses
from a particular pulser 302.sub.I to multiple of the signal paths
313.sub.0-313.sub.K-1 at the same time; and multiple of the pulsers
302.sub.0-302.sub.K-1 generating pulses for the same signal path
313.sub.k at the same time. In the example implementation shown,
routing of the signals CP.sub.0-CP.sub.L-1 among the signal paths
313.sub.0-313.sub.K-1 is controlled by digital control signals
out_slct.sub.0-out_slct.sub.L-1 from the pulsers
302.sub.0-302.sub.L-1. In another implementation, the output
manager 360 may be operable to autonomously determine the
appropriate routing (e.g., where the quantum algorithm description
includes instructions to be loaded into memory of, and executed by,
the output manager 360). In an example implementation, at any given
time, the output manager 360 is operable to concurrently route K of
the digital signals CP.sub.0-CP.sub.L-1 as K independent outbound
pulses, concurrently route K/2 of the digital signals
CP.sub.0-CP.sub.L-1 as two-pulse pairs, or route some of signals
CP.sub.0-CP.sub.L-1 as independent outbound pulses and some others
of the signals CP.sub.0-CP.sub.L-1 as multi-pulse sets (at
different times and/or concurrently).
[0050] The digital manager 354 comprises circuitry operable to
process and/or route digital control signals
(DigCtrl.sub.0-DigCtrl.sub.J-1) to various circuits of the quantum
controller 210 and/or external circuits coupled to the quantum
controller 210. In the example implementation shown, the digital
manager receives, from each pulser 302.sub.I, (e.g., via one or
more of signal paths 304.sub.0-304.sub.N-1 a digital signal D.sub.I
that is to be processed and routed by the digital manager 354, and
a control signal D_port.sub.I that indicates to which output
port(s) of the digital manager 354 the signal D.sub.I should be
routed. The digital control signals may be routed to, for example,
any one or more of circuits shown in FIG. 3B, switches/gates which
connect and disconnect the outputs AO.sub.0-AO.sub.K-1 from the
quantum processor 218, external circuits coupled to the quantum
controller 210 such as microwave mixers and amplifiers, and/or any
other circuitry which can benefit from on real-time information
from the pulser circuits 302.sub.0-302.sub.L-1. Each such
destination of the digital signals may require different operations
to be performed on the digital signal (such as delay, broadening,
or digital convolution with a given digital pattern). These
operations may be performed by the digital manager 354 and may be
specified by control signals from the pulsers
302.sub.0-302.sub.L-1. This allows each pulser 302.sub.I to
generate digital signals to different destinations and allows
different ones of pulsers 302.sub.0-302.sub.L-1 to generate digital
signals to the same destination while saving resources.
[0051] The synchronization manager 366 comprises circuitry operable
to manage synchronization of the various circuits shown in FIG. 3B.
Such synchronization is advantageous in a modular and dynamic
system, such as quantum controller 210, where different ones of
pulsers 302.sub.0-302.sub.L-1 generate, receive, and process pulses
to and from different quantum elements at different times. For
example, while carrying out a quantum algorithm, a first pulser
circuit 302.sub.1 and a second pulser circuit 302.sub.2 may
sometimes need to transmit pulses at precisely the same time and at
other times transmit pulses independently of one another. In the
example implementation shown, the synchronization manager 366
reduces the overhead involved in performing such
synchronization.
[0052] The data exchange circuitry 364 is operable to manage
exchange of data among the various circuits shown in FIG. 3B. For
example, while carrying out a quantum algorithm, first pulser
circuit 302.sub.1 and a second pulser circuit 302.sub.2 may
sometimes need to exchange information. As just one example, pulser
302.sub.1 may need to share, with pulser 302.sub.2, the
characteristics of an inbound signal AI.sub.1 that it just
processed so that pulser 302.sub.2 can generate a raw outbound
pulse CP'.sub.2 based on the characteristics of AI.sub.1. The data
exchange circuitry 364 may enable such information exchange. In an
example implementation, the data exchange circuitry 364 may
comprise one or more registers to and from which the pulsers
302.sub.0-302.sub.L-1 can read and write.
[0053] The I/O manager 368 is operable to route information between
the quantum controller 210 and the quantum programming subsystem
202.
[0054] FIG. 4 shows an example implementation of the pulser of FIG.
3B. The example pulser 302.sub.I shown comprises instruction memory
402, pulse template memory 404, digital pattern memory 406, control
circuitry 408, and compute and/or signal processing circuitry (CSP)
410.
[0055] The memories 402, 404, 406 may comprise one or more be any
type of suitable storage elements (e.g., DRAM, SRAM, Flash, etc.).
The instructions stored in memory 402 are instructions to be
executed out by the pulser 302.sub.I for carrying out its role in a
quantum algorithm. Because different pulsers 302.sub.0-302.sub.L-1
have different roles to play in any particular quantum algorithm
(e.g., generating different pulses at different times), the
instructions memory 402 for each pulser 302.sub.I may be specific
to that pulser. For example, the quantum algorithm description 206
from the quantum programming subsystem 202 may comprise a first set
of instructions to be loaded (via I/O manager 368) into pulser
302.sub.0, a second set of instructions to be loaded into pulser
302.sub.1, and so on. Each pulse template stored in memory 404
comprises a sequence of one or more samples of any arbitrary shape
(e.g., Gaussian, sinc, impulse, etc.) representing the pulses to be
sent to pulse operation circuitry 358. Each digital pattern stored
in memory 406 comprises a sequence of one or more binary values
which may represent the digital pulses to be sent to the digital
manager 354 for generating digital control signals
DigCtrl.sub.0-DigCtrl.sub.J-1.
[0056] The control circuitry 408 is operable to execute the
instructions stored in memory 402 to process inbound signal
AI.sub.I, generate raw outbound pulses CP'.sub.I, and generate
digital control signals in_slct.sub.I, out_slct.sub.I,
D_port.sub.I, D.sub.I, IF.sub.I, F.sub.I, ops_slct.sub.I,
ops_ctrl.sub.I, results.sub.I, dmod_slct.sub.I and pain. In the
example implementation shown, the processing of the inbound signal
AI.sub.I is performed by the CSP circuitry 410 and based (at least
in part) on the signal f_dmod.sub.I.
[0057] The compute and/or signal processing circuitry (CSP) 410 is
operable to perform computational and/or signal processing
functions, which may comprise, for example Boolean-algebra based
logic and arithmetic functions and demodulation (e.g., of inbound
signals All).
[0058] In operation of an example implementation, generation of a
raw outbound pulse CP'.sub.I comprises the control circuitry 408:
(1) determining a pulse template to retrieve from memory 404 (e.g.,
based on a result of computations and/or signal processing
performed by the CSP 410 ); (2) retrieving the pulse template; (3)
performing some preliminary processing on the pulse template; (4)
determining the values of F, IF, pain, ops_slct.sub.I, and
dmod_slct.sub.I to be sent to the pulse operation manager 356 (as
predetermined in the quantum algorithm description and/or
determined dynamically based on results of computations and/or
signal processing performed by the CSP 410); (5) determining the
value of ops_ctrl.sub.I to be sent to the pulse operation circuitry
358; (6) determining the value of in_slct.sub.I to be sent to the
input manager 352; (7) determining a digital pattern to retrieve
from memory 406 (as predetermined in the quantum algorithm
description and/or determined dynamically based on results of
computations and/or signal processing performed by the CSP 410);
(8) outputting the digital pattern as D.sub.I to the digital
manager along with control signal D_port.sub.I (as predetermined in
the quantum algorithm description and/or determined dynamically
based on results of computations and/or signal processing performed
by the CSP 410); (9) outputting the raw outbound pulse CP'.sub.I to
the pulse operations circuitry 358; (10) outputting results.sub.I
to the I/O manager.
[0059] FIG. 5 shows an example implementation of the pulse
operations manager and pulse operations circuitry of FIG. 3B. The
pulse operations circuitry 358 comprises a plurality of pulse
modification circuits 508.sub.0-508.sub.R-1 (R is an integer 1 in
general, and R=L/2 in the example shown). The pulse operations
manager 356 comprises control circuitry 502, routing circuitry 506,
and a plurality of modification settings circuits
504.sub.0-504.sub.K-1.
[0060] Although the example implementation has a 1-to-2
correspondence between pulse modification circuits
508.sub.0-508.sub.R-1 and pulser circuits 302.sub.0-302.sub.L-1,
that does not need to be the case. In other implementations there
may be fewer pulse modification circuits 508 than pulser circuits
302. Similarly, other implementations may comprise more pulse
modification circuits 508 than pulser circuits 302.
[0061] As an example, in some instances, two of the pullers
302.sub.0-302.sub.L-1 may generate two raw outbound pulses which
are a phase-quadrature pulse pair. For example, assuming CP.sub.1
and CP.sub.2 are a phase-quadrature pulse pair to be output on path
313.sub.3. In this example, pulse operations circuitry 358 may
process CP.sub.1 and CP.sub.2 by multiplying a vector
representation of CP'.sub.1 and CP'.sub.2 by one or more 2 by 2
matrices to: (1) perform single-sideband-modulation, as given
by
( CP 1 CP 2 ) = ( cos ( .omega. * TS * T clck 1 ) - sin ( .omega. *
TS * T clck 1 ) sin ( .omega. * TS * T clck 1 ) cos ( .omega. * TS
* T clck 1 ) ) ( CP 1 ' CP 2 ' ) , ##EQU00004##
where .omega. is the frequency of the single side band modulation
and TS is the time passed since the reference time (e.g. the
beginning of a certain control protocol); (2) keep track of
frame-of-reference rotations, as given by
( CP 1 CP 2 ) = ( cos ( .phi. ) - sin ( .phi. ) sin ( .phi. ) cos (
.phi. ) ) ( CP 1 ' CP 2 ' ) , ##EQU00005##
where .PHI. is the total phase that the frame of reference
accumulated since the reference time; and/or (3) perform an
IQ-mixer correction
( CP 1 CP 2 ) = ( C 00 C 01 C 10 C 11 ) ( CP 1 ' CP 2 ' ) ,
##EQU00006##
where C.sub.00, C.sub.01, C.sub.10, and C.sub.11 are the elements
of a matrix that corrects for IQ-mixer imperfections. In an example
implementation, each modification settings circuit, 504.sub.k,
contains registers that contain the matrix elements of three
matrices:
C k = ( C k 00 C k 01 C k 10 C k 11 ) , ##EQU00007##
an IQ-mixer correction matrix;
S k = ( cos ( .omega. * TS * T clck 1 ) - sin ( .omega. * TS * T
clck 1 ) sin ( .omega. * TS * T clck 1 ) cos ( .omega. * TS * T
clck 1 ) ) , ##EQU00008##
a single side band frequency modulation matrix; and
F k = ( cos ( .phi. ) - sin ( .phi. ) sin ( .phi. ) cos ( .phi. ) )
, ##EQU00009##
a frame rotation matrix, which rotates the IQ axes around the axis
perpendicular to the IQ plane (i.e. the z-axis if I and Q are the
x-axis and y-axis). In an example implementation, each modification
settings circuit 504.sub.k also contains registers that contain the
elements of the matrix products C.sub.kS.sub.kF.sub.k and
S.sub.kF.sub.k.
[0062] In the example shown, each pulse modification circuit
508.sub.r is operable to process two raw outbound pulses CP'.sub.2r
and CP'.sub.2r+1 according to: the modification settings
ops_cnfg.sub.2r and ops_cnfg.sub.2r+1; the signals ops_ctrl.sub.2r
and ops_ctrl.sub.2r+1; and the signals pair.sub.2r and
pair.sub.2r+1. In an example implementation pair.sub.2r and
pair.sub.2r+1 may be communicated as ops_ctrl.sub.2r and
ops_ctrl.sub.2r-1. The result of the processing is outbound pulses
CP.sub.2r and CP.sub.2r+1. Such processing may comprise adjusting a
phase, frequency, and/or amplitude of the raw outbound pulses
CP'.sub.2r and CP'.sub.2r+1. In an example implementation,
ops_cnfg.sub.2r and ops_cnfg.sub.2r+1 are in the form of a matrix
comprising real and/or complex numbers and the processing comprises
matrix multiplication involving a matrix representation of the raw
outbound pulses CP.sub.2r and CP.sub.2r+1 and the ops_cnfg.sub.2r
and ops_cnfg.sub.2r+1 matrix.
[0063] The control circuitry 502 is operable to exchange
information with the puller circuits 302.sub.0-302.sub.L-1 to
generate values of ops_confg.sub.0-ops_confg.sub.L-1 and
f_demod.sub.0-f_demod.sub.L-1, to control routing circuitry 506
based on signals ops_slct.sub.0-ops_slct.sub.L-1 and
dmod_slct.sub.0-dmod_slct.sub.L-1, and to update pulse modification
settings 504.sub.0-504.sub.K-1 based on IF.sub.0-IF.sub.L-1 and
F.sub.0-F.sub.L-1 such that pulse modification settings output to
pulse operations circuitry 358 are specifically tailored to each
raw outbound pulse (e.g., to which quantum element 222 the pulse is
destined, to which signal path 313 the pulse is destined, etc.) to
be processed by pulse operations circuitry 358.
[0064] Each modification settings circuit 504.sub.k comprises
circuitry operable to store modification settings for later
retrieval and communication to the pulse operations circuitry 358.
The modification settings stored in each modification settings
circuit 504.sub.k may be in the form of one or more two-dimensional
complex-valued matrices. Each signal path 313.sub.0-313.sub.K-1 may
have particular characteristics (e.g., non-idealities of
interconnect, mixers, switches, attenuators, amplifiers, and/or
circuits along the paths) to be accounted for by the pulse
modification operations. Similarly, each quantum element
122.sub.0-122.sub.k may have a particular characteristics (e.g.
resonance frequency, frame of reference, etc.). In an example
implementation, the number of pulse modification settings, K,
stored in the circuits 504 corresponds to the number of quantum
element 122.sub.0-122.sub.K-1 and of signal paths
313.sub.0-313.sub.K-1 such that each of the modification settings
circuits 504.sub.0-504.sub.K-1 stores modification settings for a
respective one of the quantum elements 122.sub.0-124.sub.K-1 and/or
paths 313.sub.0-313.sub.K-1. In other implementations, there may be
more or fewer pulse modification circuits 504 than signal paths 313
and more or fewer pulse modification circuits 504 than quantum
elements 122 and more or fewer signal paths 313 than quantum
elements 122. The control circuitry 502 may load values into the
modification settings circuit 504.sub.0-504.sub.K-1 via signal
503.
[0065] The routing circuitry 506 is operable to route modification
settings from the modification settings circuits
504.sub.0-504.sub.L-1 to the pulse operations circuit 358 (as
ops_confg.sub.0-ops_confg.sub.L-1 and to the pulsers
302.sub.0-302.sub.L-1 (as f_dmod.sub.0-f_dmod.sub.L1). In the
example implementation shown, which of the modification settings
circuits 504.sub.0-504.sub.K-1 has its/their contents sent to which
of the pulse modification circuits 508.sub.0-508.sub.R-1 and to
which of the pulsers 302.sub.0-302.sub.L-1 is controlled by the
signal 505 from the control circuitry 502.
[0066] The signal ops_slct.sub.I informs the pulse operations
manager 356 as to which modification settings 504.sub.k to send to
the pulse modification circuit 508.sub.I. The pulser 302.sub.I may
determine ops_slct.sub.I based on the particular quantum element
122.sub.k and/or signal path 313.sub.k to which the pulse is to be
transmitted (e.g., the resonant frequency of the quantum element,
frame of reference, and/or mixer correction). The determination of
which quantum element and/or signal path to which a particular
pulser 302.sub.I is to send an outbound pulse at a particular time
may be predetermined in the quantum algorithm description or may be
determined based on calculations performed by the pulser 302.sub.I
and/or others of the pulsers 302.sub.0-302.sub.L-1 during runtime.
The control circuitry 502 may then use this information to
configure the routing block 506 such that the correct modification
settings are routed to the correct one or more of the pulse
modification circuits 508.sub.0-508.sub.L-1.
[0067] In an example implementation, the digital signal IF.sub.I
instructs the pulse operations manager 356 to update a frequency
setting of the modification settings circuit 504.sub.k indicated by
ops_slct.sub.I. In an example implementation, the frequency setting
is the matrix S.sub.k (described above) and the signal IF.sub.I
carries new values indicating the new .omega..sub.k to be used in
the elements of the matrix S.sub.k. The new values may, for
example, be determined during a calibration routine (e.g.,
performed as an initial portion of the quantum algorithm) in which
one or more of the pulsers 302.sub.0-302.sub.L-1 sends a series of
outbound pulses CP, each at a different carrier frequency, and then
measures the corresponding inbound signals AI.
[0068] In an example implementation, the signal F.sub.I instructs
the pulse operations manager 356 to update a frame setting of the
modification settings circuit 504.sub.k indicated by
ops_slct.sub.I. In an example implementation, the frame setting is
the matrix F.sub.k (described above) and the signal F.sub.I carries
a rotation matrix F.sub.I which multiplies with F.sub.k to rotate
F.sub.k. This can be written as
F k = F l F k = ( cos ( .DELTA..phi. ) - sin ( .DELTA..phi. ) sin (
.DELTA..phi. ) cos ( .DELTA..phi. ) ) ( cos ( .phi. k ) - sin (
.phi. k ) sin ( .phi. k ) cos ( .phi. k ) ) = ( cos ( .phi. k +
.DELTA..phi. ) - sin ( .phi. k + .DELTA..phi. ) sin ( .phi. k +
.DELTA..phi. ) cos ( .phi. k + .DELTA..phi. ) ) , ##EQU00010##
where .PHI..sub.k is the frame of reference before the rotation and
.DELTA..PHI. is the amount by which to rotate the frame of
reference. The pulser 302.sub.I may determine .DELTA..PHI. based on
a predetermined algorithm or based on calculations performed by the
pulsers 302.sub.I and/or others of the pulsers
302.sub.0-302.sub.L-1 during runtime.
[0069] In an example implementation, the signal dmod_sclt.sub.I
informs the pulse operations manager 356 from which of the
modification settings circuits 504.sub.k to retrieve values to be
sent to pulser 302.sub.I as f_dmod.sub.I. The pulser 302.sub.I may
determine dmod_slct.sub.I based on the particular quantum element
122.sub.k and/or signal path 315.sub.k from which the pulse to be
processed arrived. The determination of from which quantum element
and/or signal path a particular pulser 302.sub.I is to process an
inbound pulse at a particular time may be predetermined in the
quantum algorithm description or may be determined based on
calculations performed by the pulser 302.sub.I and/or others of the
pulsers 302.sub.0-302.sub.L-1 during runtime. The control circuitry
502 may then use this information to configure the routing block
506 such that the correct modification settings are routed to the
correct one of the pulsers 302.sub.0-302.sub.L-1. For example, when
pulse generation circuit 302.sub.I needs to demodulate a pulse
signal AI.sub.I from quantum element 122.sub.k, it will send a
dmod_sclt.sub.I signal instructing the pulse operation manager 356
to rout the element
SF.sub.k00=cos(.omega..sub.k*time_stamp+.PHI..sub.k) from
modification settings circuit 504.sub.k to pulser 302.sub.I (as
f_dmod.sub.I).
[0070] In the example implementation shown, the digital signals
C.sub.0-C.sub.K-1 provide information about signal-path-specific
modification settings to be used for each of the signal paths
313.sub.0-313.sub.K-1. For example, each signal C.sub.k may
comprise a matrix to be multiplied by a matrix representation of a
raw outbound pulse CP'.sub.I such that the resulting output
outbound pulse is pre-compensated for errors (e.g., resulting from
imperfections in mixers, amplifiers, wiring, etc.) introduced as
the outbound pulse propagates along signal path 313.sub.k. The
result of the pre-compensation is that output outbound pulse
CP.sub.I will have the proper characteristics upon arriving at the
quantum processor 218. The signals C.sub.0-C.sub.K-1 may, for
example, be calculated by the quantum controller 210 itself, by the
programming subsystem 202, and/or by external calibration equipment
and provided via I/O manager 368. The calculation of signals may be
done as part of a calibration routine which may be performed before
a quantum algorithm and/or may be determined/adapted in real-time
as part of a quantum algorithm (e.g., to compensate for temperature
changes during the quantum algorithm).
[0071] FIG. 6A shows frequency generation circuitry of the quantum
controller of FIG. 3B. In the example implementation shown, the
frequency generation circuity is part of control circuitry 502 of
pulse operations manager circuitry 356. The frequency generation
circuitry comprises K coordinate rotation digital computer (CORDIC)
circuits 602.sub.0-602.sub.K-1, phase generation circuitry 604,
timestamp register 606, and S-Matrix generation circuitry 608.
[0072] Each CORDIC circuit 602.sub.k is operable to compute cosine
and sine of its input, .dwnarw..sub.k, thus generating two signals
cos(.theta..sub.k) and sin(.theta..sub.k).
[0073] The phase generation circuitry 604 is operable to generate
the CORDIC input parameters .theta..sub.0-.theta..sub.K-1 based on:
(1) the frequency setting signals IF.sub.0-IF.sub.L-1 from the
pullers 302.sub.0-302.sub.L-1; and (2) the contents, TS, of the
timestamp register 606.
[0074] The timestamp register 606 comprises circuitry (e.g., a
counter incremented on each cycle of the clock signal clk1)
operable to track the number of cycles of clk1 since a reference
point in time (e.g., power up of the quantum controller 210, start
of execution of set of instructions of a quantum algorithm by the
quantum controller 210, etc.).
[0075] In the example shown, the phase generation circuitry 604
sets .theta..sub.0=2.pi.f.sub.0(TS)(dt.sub.clk1), where f.sub.0 is
a frequency determined from the signal IF.sub.0, TS is the number
of clock cycles counted from the reference point and dt.sub.clk1 is
the duration of a single clock cycle of clk1. This leads to the
CORDIC outputs being a pair of phase-quadrature reference signals,
cos(2.pi.f.sub.0(TS)(dt.sub.clk1)) and
sin(2.pi.f.sub.0(TS)(dt.sub.clk1)), as in the example shown, which
are used to generate the S.sub.0 rotation matrix that rotates at a
frequency f.sub.0.
[0076] As shown in FIG. 6B, the signal IF.sub.I may comprise an
update component and an f.sub.I component. In an example
implementation, when update.sub.I is asserted then the phase
generation circuitry updates one of more of f.sub.0-f.sub.K-1 to be
the value of f.sub.I.
[0077] In another example implementation the phase generation
circuitry 604 can also generate CORDIC input parameters
.theta..sub.0-.theta..sub.K-1 that depend on time in a non-linear
manner in order, for example, to generate an S-matrix that rotates
at a frequency that increases or decreases in time (chirp). A chirp
is a signal of the form s(t)=cos(.omega.(t)t), meaning that the
frequency changes with time. A linear chirp can be written as
.omega.(t)=.omega..sub.0+.alpha.t at for some constant .alpha., so
that s(t)=cos(.omega.t+.alpha.t.sup.2). Note that here this
expression assumes starting the chirp at t=0. If a constant
frequency is first generated from t=0 to t=t.sub.0 and then the
chirp starts, that can be expressed as
s(t)=cos(.omega.t+.alpha.(t-t.sub.0)t). The phase of such a signal
can be written as
.theta..sub.k=2.pi.f.sub.k(TS)(dt.sub.clk1)+2.pi.(.delta.f.sub.k)(TS-TS.s-
up.C)TS*dt.sub.clk1, where .delta.f.sub.k is the change in
frequency per clock cycle of clk1 for the chirp, and TS.sup.C is
the timestamp at which the chirp is to start (and TS.sup.C=TS for
timestamps before the chirp starts). An example implementation for
a system that generates linear chirps is shown in FIG. 12. Systems
in accordance with this disclosure can generate a signal having
such a phase without having to do the whole multiplication every
time. Instead such systems can increment the phase every cycle. For
examples, as described above, in the case of a signal with a fixed
frequency (not a chirp), the phase is incremented by
.theta..sub.inc=2.pi.f.sub.k(dt.sub.clk1) every clock cycle.
Similarly, in the case of a linear chirp, the phase is incremented
by
.theta..sub.inc=2.pi.f.sub.k(dt.sub.clk1)+2.pi.(.delta.f.sub.k)(TS-TS.sup-
.C) every cycle and therefore the phase increment, .theta..sub.inc,
itself can be calculated not by multiplication, but by incrementing
it by d.PHI..sub.inc=2.pi.(.delta.f.sub.k) every clock cycle. In
one implementation the phase calculation can be done by the phase
generation circuitry 604 as indicated by the pulser via the signal
IF.sub.I (indicating for example whether a chirp should be
performed and with what frequency increments). In another
implementation the frequency can be provided by the pulser itself
via the IF.sub.I signal along the chirp. In FIG. 6A, for example,
S.sub.0 could be chirped by pulser 302.sub.0 changing the frequency
f.sub.0 on each clock cycle so that
f=f.sub.0+(.delta.f.sub.0)(TS-TS.sup.C). One advantage of this
approach is that, because f.sub.0 is calculated by the pulser
302.sub.0 and pulser 302.sub.0 comprises circuitry for performing
complex calculations, then complicated chirps such as nonlinear
chirps (chirps with different rates of frequency change), can be
achieved.
[0078] The S-matrix generation circuitry 608 is operable to build
the matrices S.sub.0-S.sub.K-1 from the outputs of the CORDIC
circuits 602.sub.0-602.sub.K-1. In an example implementation, the
S-matrix generation circuit 606 is operable to synchronize changes
to the S matrices such that any matrix update occurs on a desired
cycle of clock clk1 (which may be determined by the control
information IF.sub.0-IF.sub.L-1).
[0079] With K CORDIC circuits 602.sub.k, the frequency generation
circuitry is operable to concurrently generate K S-matrices. In
instances that more than K frequencies are needed over the course
of a set of instructions, the phase generation circuit 604 is
operable to change the input parameter .theta..sub.k of one or more
of the CORDIC circuits 602.sub.0-602.sub.K-1 to stop generating one
frequency and start generating the K+1.sup.th frequency. In some
instances, it may be necessary for the new frequency to start at a
phase .theta. that would have been the phase if the new frequency
was being generated from the initial reference time (e.g., because
the new frequency would be used to address a quantum element that
has a resonance at the new frequency and that was coherent since
the reference point). In some other instances, it might be
necessary to start the new frequency from the phase that the old
frequency ended in. The phase generation circuit 604 and timestamp
register 606 enable both of these possibilities, as further
described below with reference to FIGS. 7A and 7B.
[0080] FIGS. 7A and 7B illustrate phase continuity across frequency
hops in the frequency generation circuitry of FIGS. 6A and 6B. In
FIG. 7, CORDIC 602.sub.0 was arbitrarily selected for illustrating
phase continuity, but any of the CORDICs 602.sub.0-602.sub.N-1
could be used. Similarly, as shown in FIG. 7B, a first one of the
CORDICs could have been chosen to generate f1 during the first time
interval and a second of the CORDICs could generate f1 during the
third time interval, while still providing phase continuity.
[0081] From TS=TS1 to TS=TS2, phase generation circuitry 604
generates (based on control signal IF.sub.0) a value of
.theta..sub.0 such that CORDIC 602.sub.0 generates a pair of
phase-quadrature signals at frequency f1 (i.e.,
.theta..sub.0=2.pi.(TS)(dt.sub.clk1), where dt.sub.clk1 is the
period of clk1). The two signals can be represented as
cos(.theta..sub.0) and sin(.theta..sub.0). For simplicity of
illustration, only the cosine signal is shown in FIGS. 7A and
7B.
[0082] From TS=TS3 to TS=TS4, phase generation circuitry 604
generates (based on control signal IF.sub.0) a value of
.theta..sub.0 such that CORDIC 602.sub.0 generates a pair of
phase-quadrature signals at frequency f2. As shown, the phase of
cos(.theta..sub.0) when it changes frequency to f2 at TS3 is the
phase that the signal would have been at if the signal would have
been at frequency f2 from the beginning (i.e. from the reference
point).
[0083] From TS=TS5 to TS=TS6 phase generation circuitry 604
generates (based on control signal IF.sub.0) a value of
.theta..sub.0 such that CORDIC 602.sub.0 returns to generating a
pair of phase-quadrature signals at frequency f1. As shown, the
phase of signal 702 when it returns f1 at TS5 is the phase that the
signal would have been at if the frequency never changed and CORDIC
602.sub.0 had been continuously generating f1 since TS1.
[0084] FIG. 8A illustrates an example scenario in which a pulse
CP'.sub.1 from pulser 302.sub.1 is to be upconverted to f1.
Accordingly, in FIG. 8A, based on control signal(s) IF.sub.1 from
pulser 302.sub.1, phase generation circuitry 604 has generated a
value of .theta..sub.1 that changes every clock cycle according to
f1, and S-Matrix generation circuit 608 uses the outputs of CORDIC
602.sub.1 to generate S.sub.1 (which routing circuit 506 of FIG. 5
may then route to pulse modification circuit 508.sub.1). In an
example implementation, pulse modification setting 504.sub.1 (which
includes matrix S1, which rotates with frequency f1) is selected
from among the pulse modification settings 504.sub.0-504.sub.K-1 to
be used in the pulse modification for this particular pulse. This
choice may be based on a pulse modification scheduling algorithm
that, for example, seeks to minimize the number of frequency hops
that the frequency generation circuitry of 502 has to perform
during execution of a set of instructions.
[0085] In FIG. 8B, for clarity of illustration, it is assumed the
pulse CP'.sub.1 is an independent pulse (as opposed to a two-pulse
pair, as discussed in U.S. patent application Ser. No. 16/247,115,
which is hereby incorporated herein by reference in its entirety).
Thus, as shown, pulse modification circuit 508.sub.3 upconverts the
pulse CP'.sub.1 using the first element of the S.sub.1 matrix,
S.sub.1_00, to generate CP.sub.1. For clarity of illustration the
other modifications which may be performed in pulse modification
circuitry 508.sub.1 (e.g., multiplication by the F and C matrices
described above) are not shown in FIG. 8B.
[0086] FIG. 9 shows configuration of the frequency generation
circuitry of FIGS. 6A and 6B to support sample rates higher than
the frequency of the clock, clk1, that clocks the frequency
generation circuitry of 502. In FIG. 9, each CORDIC 602.sub.k (k an
integer between 0 and K-1) of FIG. 6A is replaced by N CORDICs
602.sub.k.sup.0-602.sub.k.sup.N-1 (only
602.sub.0.sup.0-602.sub.0.sup.N-1 are shown for simplicity of
illustration), and each S matrix S.sub.k, is replaced by N S
matrices S.sub.k.sup.0-S.sub.k.sup.N-1.
[0087] For the CORDICS 602.sub.k.sup.0-602.sub.k.sup.N-1, the phase
generation circuitry generates N phase parameter values, where each
is given by
.theta..sub.k.sup.n=2.pi.f.sub.k(TS)(dt.sub.clk1)+(n/N)2.pi.f.su-
b.k(dt.sub.clk1), and f.sub.k is the frequency instructed by
IF.sub.k, TS is the value of the timestamp register 606,
dt.sub.clk1 is the period of clk1, N is an integer upsampling
factor, and n is an integer from 0 to N-1. Thus, the CORDICs
602.sub.0.sup.0-602.sub.0.sup.N-1 generate N pairs of signals with
each pair having a phase offset of (n/N)2.pi.f.sub.0(dt.sub.clk1)
relative to the previous pair. The S matrix generation circuitry
608 then generates N S matrices from the N signal pairs.
[0088] FIGS. 10A and 10B illustrate upconversion of a quantum
control pulse in an example implementation of this disclosure. The
scenario illustrated in FIGS. 10A and 10B is the same as in FIGS.
8A and 8B, except that CP.sub.1 is required to be at a sample rate
that is N times higher than the frequency of clk1. To generate a
signal at a sample rate f_clk2=N(f_clk1), N CORDICS are configured
to generate N S-matrices S.sub.1.sup.0-S.sub.1.sup.N-1 all of which
are changing with frequency f1, but each with a diferent phase
offset and the offset of CORDIC 602.sub.1.sup.n is given by
(n/N)2.pi.f.sub.0(dt.sub.clk1)).
[0089] As shown in FIG. 10B, the matrices
S.sub.1.sup.0-S.sub.1.sup.N-1 are routed to pulse modification
circuit 508.sub.1, where each of N samples of CP'.sub.1
(CP'.sub.1_0-CP'.sub.1_N-1) is upconverted using a respective one
of the S matrices S.sub.1.sup.0-S.sub.1.sup.N-1 to generate the
signals CP.sub.1_0-CP.sub.1_N-1. Then interface circuit 902 which
is a part of output manager 360 and is clocked at f_clk2,
cyclically selects samples of 903.sup.0-903.sup.N-1 to be output as
DO.sub.1 (e.g., may select CP.sub.1_n-1 when TS % N=n) on each
cycle of clk2.
[0090] FIG. 11 shows another example configuration of the frequency
generation circuitry of FIGS. 6A and 6B to support higher output
sample rates. The example implementation in FIG. 11 uses a single
CORDIC circuit 602 as compared to N CORDIC circuits in the example
implementation of FIG. 9.
[0091] In FIG. 11, the phase generation circuitry 604 is operable
to generate, for each set of n CORDICs
602.sub.k.sup.0-602.sub.k.sup.N-1 (k an integer from 0 to K), phase
parameter .theta..sub.k.sup.0 (e.g., stored in a register 1104) and
phase increment parameters
.DELTA..sub.k.sup.1-.DELTA..sub.k.sup.N-1 (e.g., stored in a
register 1106), where
.DELTA..sub.k.sup.n=(n/N)2.pi.f.sub.0(dt.sub.clk1). For simplicity
of illustration only k=0 is shown in FIG. 11.
[0092] In operation, a change of the S matrices begins with the
phase generation circuitry 604 sequentially outputting each of
.DELTA..sub.k.sup.1-.DELTA..sub.k.sup.N-1 to the CORDIC 602.sub.k
to generate rotation parameters cos(.DELTA..sub.k.sup.1),
sin(.DELTA..sub.k.sup.1), . . . cos(.DELTA..sub.k.sup.N-1),
sin(.DELTA..sub.k.sup.N-1), which are then input, respectively to
phase rotator circuits 1102.sub.k.sup.0-1102.sub.k.sup.N-1 (e.g.,
written to registers of the phase rotator circuits
1102.sub.k.sup.0-1102.sub.k.sup.N-1.
[0093] Once, the rotation parameters have been generated, the phase
generation circuit 604.sub.k begins outputting
.theta..sub.k.sup.0=2f.sub.0(TS)dt.sub.clk1 to CORDIC 602.sub.k, to
generate cos(.theta..sub.k.sup.0) and sin(.theta..sub.k.sup.0)
which are then output to the S-matrix generation circuit 608 and to
each of the phase rotation circuits
1102.sub.k.sup.1-1102.sub.k.sup.N-1. Each phase rotation circuit
1102.sub.0.sup.n then performs a multiplication of the matrix
( cos ( .DELTA. k n ) - sin ( .DELTA. k n ) sin ( .DELTA. k n ) cos
( .DELTA. k n ) ) ##EQU00011##
by the vector
( cos ( .theta. k 0 ) sin ( .theta. k 0 ) ) ##EQU00012##
to generate cos(.theta..sub.k.sup.n) and sin(.theta..sub.k.sup.n),
where
.theta..sub.k.sup.n=.theta..sub.k.sup.0+.DELTA..sub.k.sup.n.
[0094] FIG. 12 shows an example frequency generation circuitry
operable to generate chirps. In an example implementation, FIG. 12,
the signal IF.sub.I comprises two additional signals beyond those
shown in FIG. 6B: (1) chirp.sub.I, which indicates when a chirp is
to start (e.g., is high during a chirp and low otherwise); and (2)
.delta.f.sub.I which indicates the rate of frequency change for the
chirp (a positive value of .delta.f.sub.k resulting in an upchrip
and a negative value of .delta.f.sub.k resulting in a down chirp).
The phase generation circuitry 604 then generates
.theta..sub.k=2.pi.f.sub.k(dt.sub.clk1)+2.pi.(.delta.f.sub.k)(TS-TS.sub.k-
.sup.C)(TS)dt.sub.clk1, where TS.sub.k.sup.C is the clock cycle at
which the chirp starts. When a chirp is not in progress (e.g.,
indicated by chirpk being low) then the second term in
.theta..sub.k is 0, resulting in a constant frequency signal. In an
example implementation, .theta.f.sub.k may be fixed for each chirp.
In another example implementation, the phase generation circuitry
604 may reach .delta.f.sub.k on each clock cycle for which chirp is
high and thus the puller that is generating .delta.f.sub.k can
manipulate .delta.f.sub.k to achieve non-linear chirps.
[0095] In accordance with an example implementation of this
disclosure, a quantum controller (e.g., 210) comprising quantum
control pulse generation circuitry (e.g., Pulsers
302.sub.0-302.sub.L-1), signal generation circuitry (e.g.,
602.sub.0-604.sub.K-1), and phase parameter generation circuitry
(e.g., 604). The quantum control pulse generation circuitry is
operable to generate a sequence of two quantum control pulses
(e.g., CP.sub.0,T1, CP.sub.0,T2). The phase parameter generation
circuitry is operable to determine, based on an output of the
time-tracking circuitry, a first value of a phase parameter (e.g.,
2.pi.f.sub.kTS1*dt.sub.clk1) to be used for generation of an
oscillating signal (e.g., S.sub.I_00 of FIG. 8B). The signal
generation circuitry is operable to, at a first time (e.g., TS1 of
FIG. 7A), begin generation of the oscillating signal for modulation
of a first of the two quantum control pulses; at a second time
(e.g., TS2 of FIG. 7A) after the first time , cease generation of
the oscillating signal; and at a third time (e.g., TS5 of FIG. 7A)
after the second time, resume generation of the oscillating signal
for modulation of the second quantum control pulse, wherein the
phase of the oscillating signal is determined by the value of the
phase parameter such that the phase of the oscillating signal is as
it would have been if the oscillating signal had been generated
continuously since the reference time. The output of the
time-tracking circuitry (e.g., 606) may correspond to an amount of
time lapsed between since a reference time. The time-tracking
circuitry may comprise a register (e.g., 606) operable to store a
value and increment the value on each cycle of a clock that also
clocks the signal generation circuitry (e.g., clk1). The signal
generation circuitry may comprises a plurality of signal generation
units (e.g., 602.sub.0-604.sub.K-1) in parallel. From the first
time to the second time , the oscillating signal may be generated
by a first of the signal generation units (e.g., 602.sub.0), and
from the third time to a fourth time , the oscillating signal is
generated by the first of the signal generation units.
Alternatively, From the first time to the second time , the
oscillating signal may be generated by a first of the signal
generation units (e.g., 602.sub.0), and from the third time to a
fourth time , the oscillating signal is generated by a second of
the signal generation units (e.g., 602.sub.1). The phase parameter
generation circuitry may be operable to generate N-1 phase offset
values (e.g., (n/N)2.pi.f.sub.kT_clk1, for n from 0 to N-1) to be
used for generation of the oscillating signal from the first time
to the second time, where N is an integer greater than 1. The
signal generation circuitry may comprise N signal generation units
(e.g., 602.sub.0.sup.0-602.sub.0.sup.N-1) From the first time to
the second time , each of N-1 of the signal generation units may
generate cosine and sine values based on the first value of the
phase parameter and a respective one of the N-1 phase offset
values. Each of the N signal generation units may be a CORDIC
circuit. The N signal generation units may comprise N-1 phase
rotator circuits (e.g., 1102.sub.0.sup.1-1102.sub.0.sup.N-1) and
only one CORDIC circuit (e.g., 602.sub.0). The quantum controller
may comprise matrix generation circuitry (e.g., 608) operable to
generate a matrix from the output of the signal generation
circuitry. The phase parameter generation circuitry may be operable
to determine an amount by which to increase or decrease the phase
parameter based on a value (e.g. value of f.sub.I) received from
the quantum control pulse generation circuitry. The quantum control
pulse generation circuity may be operable to calculate the value
during runtime based on a feedback signal (e.g., AI.sub.I) from a
quantum system (e.g., 218). The phase parameter generation
circuitry may be operable to generate the value of the phase
parameter based on a control signal (e.g., IF.sub.I) from the
quantum control pulse generation circuitry. The control signal may
indicate a frequency at which the oscillating signal should be
generated (e.g. as a value of component f.sub.I).
[0096] The present method and/or system may be realized in
hardware, software, or a combination of hardware and software. The
present methods and/or systems may be realized in a centralized
fashion in at least one computing system, or in a distributed
fashion where different elements are spread across several
interconnected computing systems. Any kind of computing system or
other apparatus adapted for carrying out the methods described
herein is suited. A typical implementation may comprise one or more
application specific integrated circuit (ASIC), one or more field
programmable gate array (FPGA), and/or one or more processor (e.g.,
.times.86, .times.64, ARM, PIC, and/or any other suitable processor
architecture) and associated supporting circuitry (e.g., storage,
DRAM, FLASH, bus interface circuits, etc.). Each discrete ASIC,
FPGA, Processor, or other circuit may be referred to as "chip," and
multiple such circuits may be referred to as a "chipset." Another
implementation may comprise a non-transitory machine-readable
(e.g., computer readable) medium (e.g., FLASH drive, optical disk,
magnetic storage disk, or the like) having stored thereon one or
more lines of code that, when executed by a machine, cause the
machine to perform processes as described in this disclosure.
Another implementation may comprise a non-transitory
machine-readable (e.g., computer readable) medium (e.g., FLASH
drive, optical disk, magnetic storage disk, or the like) having
stored thereon one or more lines of code that, when executed by a
machine, cause the machine to be configured (e.g., to load software
and/or firmware into its circuits) to operate as a system described
in this disclosure. As used herein, the term "based on" means
"based at least in part on." For example, "x based on y" means that
"x" is based at least in part on "y" (and may also be based on z,
for example).
[0097] While the present method and/or system has been described
with reference to certain implementations, it will be understood by
those skilled in the art that various changes may be made and
equivalents may be substituted without departing from the scope of
the present method and/or system. In addition, many modifications
may be made to adapt a particular situation or material to the
teachings of the present disclosure without departing from its
scope. Therefore, it is intended that the present method and/or
system not be limited to the particular implementations disclosed,
but that the present method and/or system will include all
implementations falling within the scope of the appended
claims.
* * * * *