U.S. patent application number 15/813442 was filed with the patent office on 2018-11-22 for photon generator.
The applicant listed for this patent is Government of the United States, as represented by the Secretary of the Air Force, Government of the United States, as represented by the Secretary of the Air Force. Invention is credited to PAUL M. ALSING, MICHAEL L. FANTO, STEFAN F. PREBLE, JEFFREY A. STEIDLE, CHRISTOPHER C. TISON.
Application Number | 20180335570 15/813442 |
Document ID | / |
Family ID | 64271563 |
Filed Date | 2018-11-22 |
United States Patent
Application |
20180335570 |
Kind Code |
A1 |
FANTO; MICHAEL L. ; et
al. |
November 22, 2018 |
PHOTON GENERATOR
Abstract
The invention provides an apparatus for optical integrated
on-chip generation of photon pairs as a building block to create
entangled photon states required for quantum information
processing. The invention provided a frequency selective optical
coupling device which controls the transmission of light by varying
the relative dimensions of otherwise symmetrical linear optical
waveguides tangential to an annular optical waveguide, thereby
controlling the coupling of light between the linear optical
waveguides and the annular optical waveguide. Dimensional change of
the optical waveguides is achieved by a heated medium in proximity
of the optical waveguides and under electronic control.
Inventors: |
FANTO; MICHAEL L.; (ROME,
NY) ; ALSING; PAUL M.; (CHITTENANGO, NY) ;
TISON; CHRISTOPHER C.; (ROME, NY) ; PREBLE; STEFAN
F.; (ROCHESTER, NY) ; STEIDLE; JEFFREY A.;
(SHARON HILL, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Government of the United States, as represented by the Secretary of
the Air Force |
Rome |
NY |
US |
|
|
Family ID: |
64271563 |
Appl. No.: |
15/813442 |
Filed: |
November 15, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62424739 |
Nov 21, 2016 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F 1/225 20130101;
G02F 2203/055 20130101; G02B 6/26 20130101; G02F 1/3132 20130101;
G02B 6/12 20130101 |
International
Class: |
G02B 6/26 20060101
G02B006/26; G02B 6/12 20060101 G02B006/12; G02F 1/225 20060101
G02F001/225; G02F 1/313 20060101 G02F001/313 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0002] The invention described herein may be manufactured and used
by or for the Government for governmental purposes without the
payment of any royalty thereon.
Claims
1. A frequency selective optical coupling device, comprising: an
annular optical channel; a first linear optical channel having a
first input and a first output, said first linear optical channel
being substantially tangential to said annular optical channel at a
first point and a second point; a second linear optical channel
having a second input and a second output, said second linear
optical channel being substantially tangential to said annular
optical channel at a third point and a fourth point; and a
predeterminable relative phase delay between said first and said
second linear optical channels, so as to cause a variance in an
amount of light traversing said first and said second linear
optical channels as a function of the frequency of said light.
2. The frequency selective optical coupling device of claim 1,
wherein said substantial tangentiality permits a coupling of light
between said annular optical channel and said linear optical
channels at said first, said second, said third and said fourth
points.
3. The frequency selective optical coupling device of claim 1,
wherein said predeterminable relative phase delay is induced by a
relative difference in length between said first linear optical
channel and said second linear optical channel.
4. The frequency selective optical coupling device of claim 3,
wherein said relative difference in length is induced by thermal
expansion.
5. The frequency selective optical coupling device of claim 4,
wherein said thermal expansion is induced by a heated medium in
proximity of said channels.
6. A photon generator device, comprising: an annular optical
channel disposed in a chip; a first linear optical channel disposed
in said chip, said channel having a first input and a first output,
said first input and a first output being in common with each other
and with an input to said chip; said first linear optical channel
being substantially tangential to said annular optical channel at a
first point and a second point; a second linear optical channel
disposed in said chip, said channel having a second input and a
second output, said second linear optical channel being
substantially tangential to said annular optical channel at a third
point and a fourth point; a first predeterminable relative phase
delay between said first and said second linear optical channels,
so as to cause a variance in an amount of light traversing said
first and said second linear optical channels as a function of the
frequency of said light; a second predeterminable relative phase
delay between said second input and said second output; a photon
detector sampling each of said second input and said second output;
a third output of said chip in common with said second input; a
fourth output of said chip in common with said second output; and
an electronic control subsystem in operative communication with
said chip for facilitating said predeterminable relative phase
delays and said photon detection.
7. The photon generator device of claim 9, wherein said substantial
tangentiality permits a coupling of light between said annular
optical channel and said linear optical channels at said first,
said second, said third and said fourth points.
8. The photon generator device of claim 9, wherein said first
predeterminable relative phase delay is induced by a relative
difference in length between said first linear optical channel and
said second linear optical channel.
9. The photon generator device of claim 9, wherein said second
predeterminable relative phase delay is induced by a relative
difference in the length of optical channel from said second input
to said third output, and the length of optical channel from said
second output to said fourth output.
10. The photon generator device of claim 11 or claim 12 wherein
said relative difference in length is induced by thermal
expansion.
11. The photon generator device of claim 13, wherein said thermal
expansion is induced by a heated medium in proximity of said
optical channels.
Description
PRIORITY CLAIM UNDER 35 U.S.C. .sctn. 119(e)
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119(e) of U.S. Provisional Patent Application Ser. No. 62/424,739
filed on Nov. 21, 2016, the entire content of which is incorporated
herein by reference.
TECHNICAL FIELD OF THE INVENTION
[0003] This invention relates generally to the field of quantum
information processing and more specifically to integrated photonic
devices that facilitate the same.
BACKGROUND OF THE INVENTION
[0004] Integrated photonics is proving to be a very promising
platform for quantum information processing. Micro ring resonators
are becoming a key component of such systems as they have been
shown to be effective as photon-pair sources by means of exploiting
a materials nonlinearity for spontaneous parametric downconversion
(SPDC) or spontaneous four wave mixing (SFWM).
[0005] Often, it is desirable to have precisely one photon. While
SPDC and SFWM sources generate pairs of photons, single photons can
be achieved through heralding. Heralding is a technique in which
the detection of a single photon from a pair is used to determine
the existence of the other. One of the fundamental issues with ring
resonators is their inherent 50% loss when critically coupled,
regardless of operation in a single bus or double bus
configuration. For single bus resonators (not shown), half of the
generated photons are lost to scattering within the cavity.
[0006] Referring to FIG. 1 depicts prior art double bus resonators
which are slightly different as the photons are free to leave the
ring 10 through either port--resulting in an effective loss of 50%.
All of this assumes that the ring resonator is critically coupled
to straight waveguides 20, 30.
[0007] As with the two typical forms of ring resonators, they are
denoted by the number of waveguides which near them giving them the
titles of single bus and double bus, respectively. Both resonators
work on the same principle. When light after a full round trip
around the ring is of equal intensity and opposite phase to light
that is reflecting into the ring, there is a destructive
interference and no light can leave the resonator. Running time in
reverse and seeing the light from the ring split at the directional
coupler is an equivalent way to view this effect. In the case of
the single bus resonator with no loss, resonance can only happen
for a coupling ratio of 50/50 from the bus waveguide. When loss is
present, this can happen for much lower splitting ratios. One form
that loss can take is scattering. The double bus resonator can be
seen as a special case of the single bus resonator where the
scattering is captured into the second waveguide.
[0008] When the ring resonator is used for generation of single
photons, two pump photons are absorbed and two single photons of
equal energy to the pumps are created. Consequentially, the single
photon light which is generated inside of the cavity has no input
light to interfere with. Still referring to FIG. 1, therefore, in
the case of the double bus resonator with the same coupler on input
and output, the light has an equal probability of exiting the first
20 and second 30 waveguide buses. This splitting is witnessed as
intrinsic loss. In the case of single bus ring resonators, the
light can either leave through the input port or be lost inside the
ring. When the pump wavelengths are optimally coupled, the
propagation losses around the ring balance with the coupling out of
the ring. The generated single photons (like the pumps) will have
this same balance in terms of loss and ability to couple out of the
ring. In other words, the single photons leave the ring only 50% of
the time. The odds of the single photons leaving the ring can be
improved at the cost of how well the pump wavelengths are coupled.
This is a compromise between loss and generation rate.
[0009] The underlying issue of single and double bus ring
resonators is that they do not have wavelength discriminating
couplers. It is well understood there doesn't exist dichroic
mirrors on a chip presently. Moreover, in 1995, Barbarossa found
that resonant wavelengths of a micro ring cavity could
theoretically be suppressed by coupling the input waveguide to the
ring at two points. However Barbarossa's design provided an optical
filter for classical light without generating any photons in the
resonator cavity. What is lacking in prior work and therefore still
needed is a device that generates entangled pairs of photons and
interferometric coupling as a filter for quantum states of
light.
OBJECTS AND SUMMARY OF THE INVENTION
[0010] It is therefore a primary object of the present invention to
provide an apparatus and method to generate entangled pairs of
photons for use in quantum information processing.
[0011] It is another object of the present invention to provide an
integrated photonic apparatus and method that generates entangled
pairs of photons.
[0012] In a fundamental embodiment of the present invention, a
frequency selective optical coupling device, comprises an annular
optical channel, a first linear optical channel having a first
input and a first output where the first linear optical channel is
substantially tangential to the annular optical channel at a first
point and a second point, a second linear optical channel having a
second input and a second output, where the second linear optical
channel is substantially tangential to the annular optical channel
at a third point and a fourth point; and a predeterminable relative
phase delay between the first and the second linear optical
channels so as to cause a variance in an amount of light traversing
the first and the second linear optical channels as a function of
the frequency of the light.
[0013] In the preferred embodiment of the present invention, a
photon generator device comprises an annular optical channel
disposed in a chip, a first linear optical channel disposed in the
chip, where the channel has a first input and a first output and
where the first input and a first output are in common with each
other and with an input to the chip, where the first linear optical
channel is substantially tangential to the annular optical channel
at a first point and a second point, and where a second linear
optical channel is disposed in the chip with the second linear
optical channel having a second input and a second output, where
the second linear optical channel is substantially tangential to
the annular optical channel at a third point and a fourth point, a
first predeterminable relative phase delay between the first and
the second linear optical channels so as to cause a variance in an
amount of light traversing the first and the second linear optical
channels as a function of the frequency of said light, and a second
predeterminable relative phase delay between the second input and
the second output, a photon detector sampling each of the second
input and the second output, and a third output of the chip in
common with the second input, a fourth output of the chip in common
with the second output, and an electronic control subsystem in
operative communication with the chip for facilitating the
predeterminable relative phase delays and the photon detection.
[0014] Briefly stated, the invention provides an apparatus for
optical integrated on-chip generation of photon pairs as a building
block to create entangled photon states required for quantum
information processing. The invention provided a frequency
selective optical coupling device which controls the transmission
of light by varying the relative dimensions of otherwise
symmetrical linear optical waveguides tangential to an annular
optical waveguide, thereby controlling the coupling of light
between the linear optical waveguides and the annular optical
waveguide. Dimensional change of the optical waveguides is achieved
by a heated medium in proximity of the optical waveguides and under
electronic control.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a prior art double bus resonator showing the
coupling coefficients to the two waveguides.
[0016] FIG. 2a is a Dual Mach-Zehnder device design of the present
invention.
[0017] FIG. 2b is a microscope image of a fabricated Dual
Mach-Zehnder device of the present invention.
[0018] FIG. 3 is a Dual Mach-Zehnder theoretical spectrum showing
suppressed resonances at the input side.
[0019] FIG. 3b is a Dual Mach-Zehnder theoretical spectrum showing
output side transmission.
[0020] FIG. 4 is a Dual Mach-Zehnder experimentally generated
spectrum showing suppressed resonances.
[0021] FIG. 5a is a Dual Mach-Zehnder measured photon pairs in the
untuned configuration.
[0022] FIG. 5b is a Dual Mach-Zehnder measured photon pairs in the
tuned configuration.
[0023] FIG. 6 is an embodiment of the present invention employing a
Dual Mach-Zehnder used to produce energy-time entangled photons
pairs/squeezed beams.
[0024] FIG. 7 is an embodiment of the present invention employing a
Dual Mach-Zehnder used to produce N00N states or pairs/squeezed
beams.
[0025] FIG. 8 is an embodiment of the present invention employing a
Dual Mach-Zehnder used to produce N00N states and pairs/squeezed
beams simultaneously.
[0026] FIG. 9 is an embodiment of the present invention employing a
Dual Mach-Zehnder used to produce N00N states, frequency combs, and
pairs/squeezed beams simultaneously.
[0027] FIG. 10 is an embodiment of the present invention employing
a Dual Mach-Zehnder used to produce N00N states, frequency combs,
and pairs/squeezed beams simultaneously.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] An object of the present invention is to devise a wavelength
dependent means to split light. The present invention employs a
Dual Mach-Zehnder (MZI) device having legs that are grossly
misbalanced, wherein the MZI will have a wavelength dependence to
its ability to split light. The present invention devises two
unbalanced MZI, one which will perfectly transmit the pump
wavelengths and partially reflect the signal wavelength. The other
MZI will do the opposite, reflecting the pump wavelengths but
perfectly transmitting the signal wavelength.
[0029] Referring to FIG. 2a and FIG. 2b, the present invention
essentially makes a Mach-Zehnder interferometer (MZI) out of the
input waveguide 40 and the ring 50. Being a cavity, the ring 50
will only support specific wavelengths of light (where the
resonance condition is satisfied) separated by the free spectral
range (FSR). The spectrum of an unbalanced MZI is sinusoidal with
the difference in optical path length between the two paths
determining where in the spectrum the constructive and destructive
interference will occur. For both the ring and the MZI, this is
known as phase-matching. For the case of the ring this is
phase-matching between consecutive round-trips while in the MZI it
is phase-matching between the two different paths. The points of
constructive interference in the spectra of these devices can be
tuned by adjusting the relative phase between the different paths.
In a fabricated device (see FIG. 2b) this can be accomplished by
heaters or electro-optic phase shifters. The combination of these
two elements results in a phase-matching condition that relies on
both the resonance condition of the ring 50 and the interference
pattern of the MZI. If the spectral width between two wavelengths
of constructive interference in the MZI is twice the FSR of the
ring 50, it is possible to suppress every second resonance of the
ring 50.
[0030] For the case of the photon-pair source function of the
present invention, one side of the ring 50 can be used as the input
40 for the pump photons and the drop side 60 as the output for the
generated photon-pairs. The MZI on the input side 40 (MZI1) can be
tuned to suppress every other resonance, while MZI2 on the output
of the ring 50 can be tuned to suppress the resonances allowed by
MZI1 (i.e. they are perfectly out of phase with each other). This
configuration will ensure the pump laser is critically coupled into
the ring 50 while not allowing it to exit out the drop port 60, and
ensures that any photons that are generated at the resonances
allowed by the drop port 60 will only exit the over-coupled drop
port (because MZI1 is tuned to not be phased matched with those
photons). This makes the device function as though it is two
independent single bus ring resonators, one for the input side and
one for the output side. The input side ring is characterized by
the transmission from the input port 40 to the through port 70
while the output side ring is characterized by the transmission
from the add port 80 to the drop port 60. The theoretical spectral
response for both the input and output sides are shown in FIG. 3a
and FIG. 3b, respectively. This configuration has three key
features: (i) The pump is critically coupled so the photon
generation rate will be maximized; (ii) The pump is filtered from
the photons that exit the drop port minimizing noise and reducing
the amount of off-chip filtering required; (iii) The photon pairs
will always leave out the same over-coupled drop port, yielding
100% coincidence ratio, maximizing heralding efficiency.
[0031] The theory of operation of the present invention has been
experimentally proven as shown in FIG. 4. The invention exhibits
all the cavity resonances when the thermal tuning has not been
optimized. When the thermal tuning has been adjusted the
undesirable resonances are suppressed as shown in FIG. 4. This
demonstrates the spectral filtering of the device, along with the
field enhancement from the ring cavity, and the directionality of
the desired output for the generated photons shown in FIG. 5a and
FIG. 5b. All aforesaid traits being useful for quantum information
science applications.
[0032] With the confirmation of the dual Mach-Zehnder configuration
as an optimal design for the generation of photon pairs, larger
photon pair states, and higher squeezed states, the functional
building block can be utilized to create entangled states when
combined with other integrated waveguide circuits.
[0033] Detailed below are five different implementations of the
present invention for quantum information science applications.
These are not the only implementations that this device can be
configured in for these applications. The invention as stated can
be used to generate, photon pairs, entangled states, larger
entangled states, and higher squeezed states (for continuous
variable applications). All embodiments of the present invention
described below can be utilized to generate any of these mentioned
photon states. Lastly another benefit of the invention is that the
source acts as filter for the pump light. This is an easy problem
to deal with in bulk optics, but in integrated circuits, removing
the pump is difficult since high rejection filters are required on
chip to deal with .about.10 orders of magnitude difference in pump
to signal power. The present invention takes care of a large
portion of this filtering.
[0034] Referring now to FIG. 6 depicts a dual Mach-Zehnder (DMZ)
source being single or bi-directionally pumped from a continuous
wave or pulsed laser source (not shown) via an optical waveguide
90. The lower diagram in FIG. 6 through FIG. 9 depicts an overlay
of the off chip electronics 160 and its associated control lines
170 (dashed lines) to detection 140 and phase shifting 150
elements.
[0035] The pump photons interact in the micro-ring resonator cavity
100 and produce signal/idler photons, which exit via the optical
waveguides 110 to the right of the micro-ring resonator 100. The
signal/idler photons pass through phase shifters 120 which can
compensate for length and timing differences before hitting an
optical tap 130 where a small portion may be sent to a
photodetector 140 to monitor the photons. The other ports 180
allows the photon pairs/squeezed beams to pass to the rest of the
circuit on the integrated chip or leave off chip. The device is
controlled by off chip electronics 160, with electrical control
lines 170 being depicted as dashed lines. Part of what the off chip
electronics 160 controls are the "heater" mechanisms 150. Heater
mechanisms 150 designated in FIG. 6 through FIG. 10 as wide, solid
black sections comprise material that is placed alongside optical
waveguide within the DMZ. When activated by the off chip
electronics, the heater mechanisms 150 heat the adjacent optical
waveguide, causing a dimensional change in the optical waveguide.
The optical dimensional change insofar as the optical waveguide
length is affected will cause a phase shift for any light therein.
The net desired effect is to alter the relative optical lengths
between the upper and lower waveguides within the DMZ.
[0036] Referring now to FIG. 7 depicts DMZ source being pumped
bi-directionally from a laser (continuous wave or pulsed) via an
optical waveguide 90. The pump photons interact in the ring
resonator 100 and produce signal/idler photons in both clockwise
and counter-clockwise directions, thus producing path
indistinguishable photons created in the ring 100. These photons
then exit via the optical waveguides 110 to the right of the ring.
The signal/idler photons pass through phase shifters 120 which can
compensate for length and timing differences before simultaneously
impinging on a directional coupler 190. This coupler 190 mixes the
photon states producing an entangled state called a N00N state, or
N photon, Zero, Zero, N photon state. The state exits the coupler
190 and passes to an optical tap 130 where a small portion may be
sent to a detector 140 to monitor the photons. The other ports 180
allows the photons to pass to the rest of the circuit on the
integrated chip or leave off chip.
[0037] Referring now to FIG. 8 depicts DMZ source being pumped
bi-directionally from a laser (continuous wave or pulsed) via an
optical waveguide 90. The pump photons interact in the ring
resonator cavity 100 and produce signal/idler photons in both
clockwise and counter-clockwise directions, thus producing path
indistinguishable photons created in the ring resonator 100. These
photons then exit via the optical waveguides 110 to the right of
the ring resonator 100. The spectrally degenerate photons are
selected by an optical ring resonator filter 200 and pass through
phase shifters 120 which can compensate for length and timing
differences before impinging on a directional coupler 190. This
coupler 190 mixes the photon states producing an entangled state
called a N00N state, or N photon, Zero, Zero, N photon state. The
state exists the coupler 190 and passes to the rest of the circuit
on the integrated chip or leave off chip. The photons that are not
selected by the filter 200 travel on a different waveguide, passing
through a phase shifter 120 and then hitting an optical tap 130.
This resonant comb of other wavelengths can be monitored with a
photodetector 140 or passed to other circuitry to be utilized
elsewhere. This source, shown in FIG. 8, can then produce N00N
states, entangled frequency combs, and or squeezed states
simultaneously.
[0038] Referring to FIG. 9 depicts The DMZ source is pumped
bi-directionally from a laser (continuous wave or pulsed) via an
optical waveguide 90. The pump photons interact in the ring
resonator cavity 100 and produce signal/idler photons in both
clockwise and counter-clockwise directions, thus producing path
indistinguishable photons created in the ring resonator 100. These
photons then exit via the optical waveguides 110 to the right of
the ring resonator 100. The spectrally degenerate photons are
selected by an optical ring resonator filter 200 and pass through
phase shifters 120 which can compensate for length and timing
differences before impinging on a directional coupler 190. This
coupler 190 mixes the photon states producing an entangled state
called a N00N state, or N photon, Zero, Zero, N photon state. The
state exits the coupler 190 and passes to the rest of the circuit
on the integrated chip or leave off chip to other circuits. The
photons that are not selected by the ring resonator filter 200
travel on a different waveguide, passing through a phase shifter
120 followed by two additional filters 210. These two secondary
filters 210 can serve a number of functions. They can further
filter the pump wavelength to allow for a filtered set of photons
to leave on the original waveguide. They can each filter out a
different set of wavelengths to produce more correlated outputs,
one on each set of filter outputs and letting the rest of the comb
exit on the original waveguide when multiple correlated outputs are
required. This source can then produce N00N states, multiple
energy-time correlated pairs/squeezed beams, entangled combs, and
squeezed states simultaneously.
[0039] Referring to FIG. 10 depicts the DMZ source being pumped
bi-directionally from a laser (continuous wave or pulsed) via an
optical waveguide 90. The pump photons interact in the ring
resonator cavity 100 and produce signal/idler photons in both
clockwise and counter-clockwise directions, thus producing path
indistinguishable photons created in the ring resonator 100. These
photons then exit via the optical waveguides to the right of the
ring resonator 100. The signal/idler photons pass through phase
shifters 120 which can compensate for length and timing differences
before simultaneously impinging on a directional coupler 190. This
coupler 190 mixes the photon states producing an entangled state
called a N00N state, or N photon, Zero, Zero, N photon state. The
state exits the coupler 190 and passes to a switching network which
in one implementation could consist of Mach-Zehnder interferometers
(MZI). These MZI's mix the photon states in a reconfigurable manner
that allows the creation of entangled states. These can range from
two photon (Bell states) to larger entangled states (Cluster and
Greene-Horne-Zeilinger (GHZ) states). The circuit can be used to
produce states important for small scale quantum information
processing, specifically quantum computation. The optical
waveguides can terminate with photodetectors 140 allowing the
entire computation to be completed on chip.
[0040] Having described preferred embodiments of the invention with
reference to the accompanying drawings, it is to be understood that
the invention is not limited to those precise embodiments, and that
various changes and modifications may be effected therein by one
skilled in the art without departing from the scope or spirit of
the invention as defined in the appended claims.
* * * * *