Quantum optical memristor

Abstract

The quantum optical memristor (1) comprises a Mach-Zehnder interferometer (2) having a first optical input (3), a first optical output (5), and a second optical output (6), a detector (9) for detecting a time-dependent optical signal n(t) at the second optical output (6) of the Mach-Zehnder interferometer (2), and a target reflectivity R of the Mach-Zehnder interferometer (2). target The first optical input (3) and the first optical output (5) of the Mach-Zehnder interferometer (2) are the first optical input (7) and the first optical output (8) of the quantum optical memristor (1), respectively. The controller (10) calculates the calculated target reflectance R target The controller 10 updates the reflectivity R(t) of the Mach-Zehnder interferometer 2 to match the target reflectivity R(t) based on the derivative of the reflectivity with respect to time. target The derivative of the reflectivity with respect to time is a linear function of the detected signal n(t).

Description

[Technical Field]

[0001] The present invention relates to a quantum optical memristor for manipulating photon quantum states. - A Mach-Zehnder interferometer having at least a first optical input and a first optical output and a second optical output, - A detector configured to detect the time-dependent optical signal n(t) at the second optical output of the Mach-Zehnder interferometer, - Target reflectance R of the Mach-Zehnder interferometer target A controller configured to calculate the The first optical input and first optical output of the Mach-Zehnder interferometer are the first optical input and first optical output of a quantum optical memristor, respectively. The controller calculates the target reflectance R target The reflectance R(t) of the Mach-Zehnder interferometer is configured to update to match the value.

[0002] The present invention also relates to a method for manipulating optical qubits using a quantum optical memristor. The quantum optical memristor is - A Mach-Zehnder interferometer having at least a first optical input, a first optical output, and a second optical output, - A detector configured to detect the time-dependent optical signal n(t) at the second optical output of the Mach-Zehnder interferometer, - Target reflectance R of the Mach-Zehnder interferometer target A controller configured to calculate the The first optical input and first optical output of the Mach-Zehnder interferometer are the first optical input and first optical output of a quantum optical memristor, respectively. The controller calculates the target reflectance R target The reflectance R(t) of the Mach-Zehnder interferometer is updated to match, This method, - The steps of supplying one or more photons to a quantum optical memristor at the optical input of a quantum optical memristor, - Measuring the optical signal n(t) in a detector; - Updating the reflectivity R(t) of a Mach-Zehnder interferometer so as to match the calculated target reflectivity R target .

Background Art

[0003] The project leading to this application has received financial support from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 820474, from the Austrian Science Fund (FWF): Forschergruppe FG5, and from the Austrian Federal Ministry of Education, Science and Research (BMBWF) and the Austrian Federal Ministry for Digital and Economic Affairs (BMDW) via their programme "QuantERA".

[0004] Memristors have been hypothesized as a fourth basic passive circuit element in addition to resistors, capacitors, and inductors. The basic characteristic of such a device is to retain the memory of its past state in the form of resistive hysteresis.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

[0006] In Non - Patent Document 1, a more general concept of memristive devices is introduced, and this memristive device is defined by the following formula.

[0007] [Number]

[0008] Here, u and y represent the input and output variables, respectively, and s represents the state variable, all of which are implicitly assumed to depend on time t. The device is first demonstrated in an electronic circuit, where u and y are current and voltage, and f is a generalized resistance. In addition to preserving quantum coherence when processing information encoded in a quantum state, a quantum memristor should be able to surpass its classical counterpart by enabling the same behavior as its classical counterpart. Depending on the choice of input and output variables, a quantum memristor must offer the following characteristics: (a) Demonstrate the dynamics of the above formula when the memoistic behavior at the classical limit is considered, i.e., when the expectation value of the quantum observable is taken into account. (b) Quantum coherent processing, i.e., the ability to coherently map a quantum input state onto an output state. These two requirements are typically mutually exclusive, which poses a serious technical obstacle. The only situation in which a quantum photon device exhibits the memory behavior required in case (a) is through interaction with the environment over some form of measurement processing. In practice, this is always associated with some level of decoherence, thus invalidating point (b) and making the device indistinguishable from a classical memristor. To overcome this contradiction, it is necessary to implement an open quantum system such that features (a) and (b) can coexist, and the interaction with the environment must be strong enough to produce effective nonlinearity, but at the same time weak enough to adequately preserve quantum coherence.

[0009] Non-Patent Literature 2 describes a quantum memristor in an electronic circuit. Non-Patent Literature 2 introduces a quantum memristor based on tunneling induced by quasiparticles and the cancellation of superconducting currents. The memristor comprises a superconducting quantum interferometer (SQUID) and a superconducting circuit. However, the electronic memristor is not suitable for photonics, i.e., the operation of optical qubits. On the other hand, the SQUID and superconducting circuit cannot process photons. On the other hand, the electronic memristor is voltage-controlled. It is essential that the voltage can take both positive and negative values, which is not the case for optical signals. Therefore, the presented algorithm is also not suitable for a photon memristor.

[0010] Non-patent document 3 presents a protocol and numerical simulations relating to a quantum electronic memristor based on a superconducting circuit. The proposed system consists of a quantum LC circuit with a shunt provided by the memristor. Therefore, this component is not suitable for processing photons. The protocol is based on measuring the voltage applied to the memristor. Again, it is essential that the voltage can take both positive and negative values, which is not the case for optical signals. Therefore, the protocol is not suitable for photon memristors.

[0011] In Non-Patent Document 4, the possibility of realizing a quantum memristor in the photon domain was pointed out. Non-Patent Document 4 proposes using a Mach-Zehnder interferometer with a tunable delay. The Mach-Zehnder interferometer operates as a tunable beam splitter, while its reflectivity is modifiable by the delay. A model is proposed for adapting the phase based on a previously detected signal. The proposed device theoretically satisfies the requirements of the memristor outlined above for coherent and squeezed states. The model shows the shift behavior for the Fock state, which is perhaps most relevant to quantum photonics applications. In those examples with the Fock state, they obtain a hysteresis diagram that does not approach the origin. Physically, they are called orthogonal phase operators, with an input quantity xin This occurs because a feedback function based on is used, but an input state with zero orthogonal phase does not always mean an output state with zero photons. Therefore, even if their proposed devices could exhibit memory behavior, this is inconsistent with the definition of a mesostatic device, and specifically, inconsistent with the required resistive hysteresis. Furthermore, the scheme proposed by Non-Patent Literature 4 is very challenging, if not impossible, to actually implement, as it requires tuning and measurement of the orthogonal phase operator, which generally requires mixing states with a coherent beam, and thus greatly complicates any experimental setup. Moreover, the input state is given by a superposition of Fock states, which is impractical, although feasible in linear optics, especially considering that the mean orthogonal phase of such states depends on its relative phase term, which should be strictly controlled. A further challenge is the fact that manipulating qubits encoded in superposition with a vacuum state is always far from trivial. Although Non-Patent Literature 4 schematically shows the measurement performed at the second output of the beam splitter, the proposed input quantity x in The method for deriving such results from such measurements is not disclosed.

[0012] Non-patent document 5 describes different implementations of quantum memristors in quantum photonics setups.

[0013] The object of the present invention is to provide a quantum optical memristor and a method that can manipulate photon quantum states. [Means for solving the problem]

[0014] This invention proposes a device as defined at the beginning, The controller (10) is the derivative of the reflectance with respect to time

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[0015] If a, b, and p are any non-zero real numbers,

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[0016] Generally, within the scope of this disclosure, the derivative of reflectance with respect to time

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[0017] Optionally, the derivative of the reflectance with respect to time

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[0018] The present invention also relates to a method as defined at the beginning, the controller (10) is configured to calculate a target reflectance R

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[0019] As a Mach-Zehnder interferometer, we can understand any device in which we can adjust the probability P1 that a photon arriving at the input is emitted at the first of two or more (M) outputs. Here,

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[0020] A Mach-Zehnder interferometer can operate as a beam splitter, and its probability can be changed by altering the relative phase of the optical paths. In this embodiment, the interferometer can operate as an adjustable beam splitter, and therefore P1 may be called the “reflectance” of the Mach-Zehnder interferometer.

[0021] In a typical embodiment, the Mach-Zehnder interferometer may be a device that splits incident light into two paths using a first beam splitter, introduces a relative phase term between the two paths, for example by a delay, and recombines the two paths in a second beam splitter. The probability P1 that an incident photon is emitted at the first of the two outputs of the Mach-Zehnder is modifiable by changing the relative phase term between the two paths. In this embodiment, the overall operation of the Mach-Zehnder interferometer is therefore equivalent to that of a tunable beam splitter.

[0022] In another preferred embodiment, the controller is the derivative of the reflectance

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[0023] It should be noted that if the lower bound of the integration interval is a (positive) function of time, this will result in a derivative containing negative terms. For example,

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[0024] Optionally, the length of the time frame T can be configured, preferably, to be less than or equal to the modulation period of the optical input signal at the optical input of the Mach-Zehnder interferometer (2). Depending on the relationship between the modulation period of the optical input signal and the integration time T, two limiting schemes are accessible. If the integration time T is small compared to the modulation period, the input may be considered nearly constant. The behavior then simplifies to R(t) = n(t) for a single photon. In contrast, if the input oscillates very quickly such that the modulation time is small compared to the integration time T, the integral approaches zero, resulting in R(t) = 0.5, which gives a constant reflectance R of 50%. If the integration time is equal to the modulation period, the integral is over the entire modulation period and therefore zero. Thus, integrating over a period longer than one results in redundant results. For this reason, the integration time is preferably less than or equal to the modulation period.

[0025] For example, the signal n(t) in the detector may relate to the number of detected photons (e.g., a photon count). This is particularly advantageous for applications involving a small number of photons, especially when the device is used to manipulate qubits encoded as single photons. The detector may be a single-photon detector (e.g., a photon counter). In a preferred embodiment, the quantum optical memristor comprises parallel paths having optical inputs and optical outputs, the optical inputs and optical outputs of the parallel paths being second optical inputs and second optical outputs of the quantum optical memristor, respectively, and the parallel paths and the Mach-Zehnder interferometer are configured to be supplied from the same photon source, and the parallel paths essentially do not manipulate the state of photons in the parallel paths. The parallel paths provide the possibility for the quantum optical memristor to transmit photons without interacting with the Mach-Zehnder interferometer. Thus, the photons may be manipulated or transmitted essentially in their original state.

[0026] Preferably, the parallel paths are configured to relate to a first spatial mode, and the Mach-Zehnder interferometer is configured to relate to a second spatial mode of the qubit, where the qubit is encoded as a single photon that is a superposition of the first and second spatial modes. Thus, the qubit may be path-coded rather than encoded as a superposition of energy states. Path-coded qubits are easier to handle in quantum optics compared to qubits encoded as a superposition of two energy levels. This embodiment greatly expands the possibilities for applications.

[0027] Preferably, the quantum optical memristor includes parallel paths having an optical input and an optical output. The optical input and output of the parallel paths are the second optical input and second optical output of the quantum optical memristor, respectively. The first and second optical inputs of the quantum optical memristor are configured to be supplied from the same photon source. Parallel paths, in essence, do not manipulate the state of photons along the parallel paths. The parallel paths are configured to relate to the first spatial mode, and the Mach-Zehnder interferometer is configured to relate to the second spatial mode of the qubit, where the qubit is encoded as a single photon which is a superposition of the first and second spatial modes. This method, - This includes supplying a quantum optical memristor with qubits encoded as photons that are a superposition of the first and second spatial modes. This method is suitable for qubits encoded as a superposition of two spatial modes, which is a particularly beneficial and natural choice in the case of integrated quantum photonics.

[0028] Optionally, the Mach-Zehnder interferometer may be equipped with two beam splitters, each having a 50 / 50 splitting ratio. To achieve maximum adjustability of reflectivity across the entire range between 0 and 1, the beam splitters should have a 50 / 50 splitting ratio.

[0029] Preferably, the quantum optical memristor is provided partially as part of an integrated photonic chip, and at least the Mach-Zehnder interferometer is part of the integrated photonic chip. The Mach-Zehnder interferometer includes two beam splitters and a delayer, which may also be part of the integrated photonic chip. The delayer is part of one of the two arms of the Mach-Zehnder interferometer and is used to change the relative phase between the two arms. Components of the quantum optical memristor, being part of the integrated photonic chip, can be manufactured in a reliable and reproducible manner, and the cost per component can be reduced. Furthermore, the optical paths are rigidly mechanically connected, thus preventing phase decoherence. At least the detector and controller are typically external components.

[0030] Optionally, the quantum optical memristor is supplied partially as part of an integrated photonic chip, with at least the Mach-Zehnder interferometer and parallel paths being part of the integrated photonic chip. Components of the quantum optical memristor, being part of the integrated photonic chip, can be manufactured in a reliable and reproducible manner, reducing the cost per component. Furthermore, the optical paths are rigidly mechanically connected, thus preventing phase decoherence. At least the detector and controller are typically external components.

[0031] In preferred embodiments, the quantum optical memristor is at least partially glass-based and laser-written to the glass, and at least the Mach-Zehnder interferometer is glass-based and laser-written to the glass. Glass is particularly suitable as a substrate and is also suitable for laser writing, which provides a high level of reproducibility.

[0032] In other preferred embodiments, the quantum optical memristor is at least partially glass-based and laser-written to glass, with at least the Mach-Zehnder interferometer and parallel paths being glass-based and laser-written to glass. Glass is particularly suitable as a substrate and is also suitable for laser writing, which provides a high level of reproducibility.

[0033] Preferably, the Mach-Zehnder interferometer comprises two beam splitters, the beam splitters being guided directional couplers. Guided directional couplers are a ready-made, reliable component in integrated photonics and are suitable for use as beam splitters according to the present invention.

[0034] In the following, preferred embodiments of a quantum optical memristor and a method for manipulating optical qubits using the quantum optical memristor according to the present invention are defined, along with preferred combinations thereof.

[0035] 1. Quantum optical memristors for manipulating photon quantum states are: - A Mach-Zehnder interferometer having at least a first optical input and a first optical output and a second optical output, - A detector configured to detect the time-dependent optical signal n(t) at the second optical output of the Mach-Zehnder interferometer, - Target reflectance R of the Mach-Zehnder interferometer target A controller configured to calculate the The first optical input and first optical output of the Mach-Zehnder interferometer are the first optical input and first optical output of a quantum optical memristor, respectively. The controller calculates the target reflectance R target The reflectance R(t) of the Mach-Zehnder interferometer is updated to match, Quantum optical memristors are, The controller is the derivative of the reflectance with respect to time.

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[0036] 2. The quantum optical memristor according to Embodiment 1 is The linear function is characterized by having a negative offset proportional to the maximum expected value of the signal n(t).

[0037] 3. The quantum optical memristor according to Embodiment 1 or 2 is The controller is the derivative of the reflectance

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[0038] 4. The quantum optical memristor according to Embodiment 3 is The length T of the time frame can be configured to be less than or equal to the modulation period of the optical input signal at the optical input of the Mach-Zehnder interferometer (2), and preferably, it is characterized by being configured in this way.

[0039] 5. A quantum optical memristor according to any one of Embodiments 1 to 4 is: The signal n(t) in the detector is characterized by being related to the number of photons detected.

[0040] 6. A quantum optical memristor according to any one of Embodiments 1 to 5 is: A parallel path having an optical input and an optical output is provided. The optical input and optical output of the parallel paths are the second optical input and second optical output of the quantum optical memristor, respectively. The parallel paths and the Mach-Zehnder interferometer are configured to be supplied from the same photon source. The parallel paths are characterized by not inherently altering the state of photons along the parallel paths.

[0041] 7. The quantum optical memristor according to Embodiment 6 is The parallel paths are configured to relate to a first spatial mode, and the Mach-Zehnder interferometer is configured to relate to a second spatial mode of the qubit, wherein the qubit is encoded as a single photon which is a superposition of the first and second spatial modes.

[0042] 8. A quantum optical memristor according to any one of embodiments 1 to 7 is: The Mach-Zehnder interferometer is equipped with two beam splitters (14,15), The beam splitter (14,15) is characterized by having a 50 / 50 splitting ratio.

[0043] 9. A quantum optical memristor relating to any one of the implementation forms 1 to 8 is: A quantum optical memristor is provided, at least partially, as part of an integrated photonic chip. At least the Mach-Zehnder interferometer is characterized by being part of an integrated photonic chip.

[0044] 10. The quantum optical memristor according to Embodiment 6 or 7 is A quantum optical memristor is provided, at least partially, as part of an integrated photonic chip. At least the Mach-Zehnder interferometer and parallel paths are characterized as being part of an integrated photonic chip.

[0045] 11. The quantum optical memristor according to Embodiment 9 or 10 is A quantum optical memristor is at least partially glass-based, and laser-written onto glass. At least the Mach-Zehnder interferometer is characterized by being glass-based and laser-written onto the glass.

[0046] 12. The quantum optical memristor according to Embodiment 10 is A quantum optical memristor is at least partially glass-based, and laser-written onto glass. At least a Mach-Zehnder interferometer and a parallel path are based on glass and laser-written onto the glass.

[0047] 13. A quantum optical memristor according to any one of embodiments 1 to 12 is: The Mach-Zehnder interferometer is equipped with two beam splitters (14,15), The beam splitter (14,15) is characterized by being a guided directional coupler (17,18).

[0048] 14. A method for manipulating optical qubits using a quantum optical memristor, Quantum optical memristors are, - A Mach-Zehnder interferometer having at least a first optical input, a first optical output, and a second optical output, - A detector configured to detect the time-dependent optical signal n(t) at the second optical output of the Mach-Zehnder interferometer, - Target reflectance R of the Mach-Zehnder interferometer target A controller configured to calculate the The first optical input and first optical output of the Mach-Zehnder interferometer are the first optical input and first optical output of a quantum optical memristor, respectively. The controller calculates the target reflectance R target The reflectance R(t) of the Mach-Zehnder interferometer is updated to match, The controller is the derivative of the reflectance with respect to time.

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[0049] 15. The method of Embodiment 14 is A quantum optical memristor has parallel paths having an optical input and an optical output. The optical input and optical output of the parallel paths are the second optical input and second optical output of the quantum optical memristor, respectively. The first and second optical inputs of the quantum optical memristor are configured to be supplied from the same photon source. Parallel paths, in essence, do not manipulate the state of photons along the parallel paths. A parallel path is configured to relate to the first spatial mode, and the Mach-Zehnder interferometer is configured to relate to the second spatial mode of the qubit, where the qubit is encoded as a single photon which is a superposition of the first and second spatial modes. Book 2, - This is characterized by supplying a qubit encoded as a photon, which is a superposition of the first and second spatial modes, to a quantum optical memristor.

[0050] The present invention will be further described below with reference to particularly preferred embodiments and drawings. However, the present invention is not intended to be limited to these embodiments. [Brief explanation of the drawing]

[0051] [Figure 1] A schematic representation of the quantum optical memristor in the first embodiment is shown. [Figure 2] A schematic diagram of a quantum optical memristor in a second embodiment having parallel paths is shown. [Figure 3] Figure 2 schematically shows an experimental setup for manipulating a single photon using a quantum optical memristor. [Figure 4] The experimental results obtained using the experimental setup shown in Figure 3 are presented. [Modes for carrying out the invention]

[0052] Figure 1 shows a quantum optical memristor 1 for manipulating photon quantum states in a first embodiment. The quantum optical memristor 1 comprises a Mach-Zehnder interferometer 2 having a first optical input 3 and a second optical input 4, and a first optical output 5 and a second optical output 6. The first optical input 3 and the first optical output 5 of the Mach-Zehnder interferometer are the first optical input 7 and the first optical output 8 of the quantum optical memristor 1, respectively. The detector 9 is configured to detect a time-dependent optical signal n(t) at the second optical output 6 of the Mach-Zehnder interferometer 2.

[0053] Furthermore, the controller 10 controls the target reflectance R of the Mach-Zehnder interferometer 2. target The controller 10 is configured to calculate the calculated target reflectance R target The controller 10 is configured to update the reflectance R(t) of the Mach-Zehnder interferometer 2 to match the time difference. The reflectance of the Mach-Zehnder interferometer is the probability that a photon changes paths 11,12 in the Mach-Zehnder interferometer 2. Thus, the controller 10 controls the phase difference of paths 11,12, and thereby controls the reflectance R(t). Means for changing the phase 13 in one of paths 11,12, such as a phase delay, are included and are controlled by the controller 10. The controller 11 controls the derivative of the reflectance with respect to time.

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[0054] The time derivative of the reflectance in this exemplary embodiment

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[0055] Based on the signal n(t), R target To estimate the derivative of the reflectance, the controller 10 uses

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[0056] The behavior of the quantum optical memristor is configurable by selecting the length T of the time frame. The length T is preferably the modulation or oscillation period T of the optical input signal at the optical input 7 of the Mach-Zehnder interferometer 2. oscThe following is selected: If a low-pass filter, such as an RC filter, is used, the integration time T must be greater than the filter's time constant. Depending on the relationship between the modulation period and length T of the optical input signal, two limiting modes are accessible. If the integration time T is small compared to the modulation period, the input may be considered (almost) constant. The behavior simplifies to R(t) = n(t). In contrast, if the input oscillates very quickly such that the modulation time is small compared to the integration time T, the integral approaches zero, resulting in R(t) = 0.5, which gives a constant reflectance R of 50%. If the integration time is equal to the modulation period, the integral is over the entire modulation period and therefore zero. Thus, integrating over a period longer than one results in redundant results. For this reason, the integration time is preferably less than or equal to the modulation period.

[0057] The signal n(t) in detector 9 is related to the number of photons detected. In this case, the detector is a single-photon detector. The Mach-Zehnder interferometer is equipped with two beam splitters 14 and 15, each with a 50 / 50 splitting ratio. This splitting ratio is particularly useful for controlling the reflectance R(t).

[0058] The quantum optical memristor 1 is partially provided as part of an integrated photonic chip 16. Specifically, the Mach-Zehnder interferometer 2, including beam splitters 14, 15 and means for changing the phase 13, such as a delay element, is part of the integrated photonic chip. The detector 9 and controller 10 are external components. By employing advanced processing and techniques known in the field of integrated photonics, the quantum optical memristor 1 can be manufactured in a reliable, stable, and reproducible manner. Furthermore, these processing methods are relatively easy to scale, resulting in a low cost per unit. Additionally, the quantum optical memristor 1 can be realized with small dimensions and intrinsic compatibility with further integrated photonic components. Moreover, the relevant components of the quantum optical memristor 1 are mechanically rigidly connected to one another via the integrated photonic chip 16. This prevents undesirable levels of phase decoherence of the qubits, which could adversely affect the properties of the quantum optical memristor 1. In this context, a thermal phase shifter may be used as a means for changing the phase 13. For example, the quantum optical memristor 1 may be glass-based and laser-written to the glass. The beam splitters 14,15 are guided directional couplers 17,18. The guided directional couplers 17,18 are off-the-shelf, reliable components in integrated photonics and are suitable for use as beam splitters 14,15 according to the present invention.

[0059] The quantum optical memristor 1 supplies one or more photons to the quantum optical memristor at the optical input 7, measures the optical signal n(t) at the detector 9, and calculates the target reflectance R target By updating the reflectivity R(t) of the Mach-Zehnder interferometer 2 to match this, it can be used to manipulate the photon quantum state.

[0060] The fabrication of the integrated photonic chip may be based on femtosecond laser micromachining. A single-mode optical waveguide optimized for operation at 1550 nm is written onto aluminoborosilicate glass (Corning EAGLE XG, 1.1 mm thick) by focusing a laser pulse (Yb:KYW cavity-dampened mode-locked laser: wavelength 1030 nm, pulse duration 300 fs, energy 520 nJ per pulse, repetition rate 1 MHz) using a 50x objective lens (0.65 NA) with an anomalous aberration correction ring. The entire optical circuit is written 25 μm from the bottom surface of the substrate by translating the substrate at a constant velocity of 40 mm / s. In particular, six overlapping laser scans are performed along the desired waveguide path. To achieve single-mode operation and reduce waveguide birefringence, thermal annealing is performed after the writing process, including a fast rise ramp that heats up to 750°C at a rate of 12°C per minute, followed by two slow fall ramps that cool down to 630°C at a rate of 12°C per hour and then to 500°C at a rate of 24°C per hour. The cooling process is then completed without controlling the temperature ramps. At the end of the waveguide fabrication process, the measured insertion loss is 1.2 dB, corresponding to 76% transmission.

[0061] The Mach-Zehnder interferometer 2 consists of two balanced directional couplers 17,18 (with zero interaction length and a coupling distance of 7.5 μm), which can be connected to the rest of the circuit by an S-shaped waveguide (radius of curvature of 40 mm) and a straight waveguide (separation p=127 μm and length L=2 mm). To ensure maximum efficiency and minimum crosstalk in the phase shift operation, thermal isolation trenches are formed by ablation on both sides of the optical waveguide, which is expected to be phase-tuned. To fabricate the trenches, a laser pulse (Light Conversion PHAROS: wavelength of 1030 nm, pulse duration of 1 picosecond, energy of 1.5 μJ per pulse, repetition rate of 20 kHz) is used, focused by a 20x water immersion objective lens (0.50 NA) at the bottom of the substrate. The latter is fully immersed in distilled water and translated at 4 mm per second. This fabrication technique is commonly referred to as water-assisted laser ablation. Depth D t =300μm, width W t =97μm, and length L t To create a single trench with L=2mm, four rectangular glass blocks (depth D b =D tThe material (75 μm) is removed alternately by ablating only the periphery of each block, separating it, and submerging it in water. In this way, deep trenches are produced on the bottom side of the substrate with a yield of approximately 1. The substrate is then flipped over, and the process continues on the bottom side by producing a thermal phase shifter. First, after a standard piranha washing bath, a multilayer metal film consisting of 3 nm chromium and 100 nm gold is deposited across the entire area of ​​the chip using a magnetron sputtering system. Secondly, to reach a stable value for electrical resistivity and to prevent electrical drift that would impair the stability of the phase shift operation, further thermal annealing is performed (a rise ramp that heats up to 500°C at a rate of 10°C per minute, a period of 60 minutes at which this temperature is maintained, and a subsequent cooling process without thermal operation). Finally, the thermal phase transfer is patterned by laser pulses (cavity-dampened mode-locked laser of Yb:KYW: wavelength 1030nm, pulse duration 300fs, energy 200nJ per 669 pulses, repetition rate 1MHz) focused on the chip surface with a 10x objective lens (0.25NA). By translating the substrate at 2mm per second, the contact pads and electrodes are isolated by selectively removing metal. In their place, width W r =pW t = 30 μm and length L r A resistive microheater with L=2mm is isolated by the presence of a trench. The average electrical resistance of the microheater is 38Ω, while the resulting power required to produce a 2π phase shift is small, around 55mW. Finally, the photonic chip is mounted on an aluminum heatsink, wire-bonded to a printed circuit board, and connected to both input and output single-mode optical fibers by pigtailing. After pigtailing, the total insertion loss from input to output fiber is 2dB, corresponding to 63% transmission.

[0062] Figure 2 shows another embodiment of the quantum optical memristor 1. In addition to the embodiment shown in Figure 1, the quantum optical memristor comprises a parallel path 19 having an optical input 20 and an optical output 21. The optical input 20 and optical output 21 of the parallel path 19 are the second optical input 22 and second optical output 2) of the quantum optical memristor 1, respectively. The parallel path 19 and the Mach-Zehnder interferometer 2 are configured to be supplied from the same photon source; in other words, the quantum optical memristor 1 is supplied from a single photon source. The parallel path 1) does not, in essence, manipulate the state of photons in the parallel path 19. Any additional components that can change the state of photons are not part of the parallel path 19. The parallel path 19 is configured to relate to a first spatial mode, and the Mach-Zehnder interferometer 2 is configured to relate to a second spatial mode of a qubit, where the qubit is encoded as a single photon that is a superposition of the first and second spatial modes. Therefore, the quantum optical memristor 1 is suited to manipulating path-encoded qubits rather than those encoded as a superposition of energy states. Path-encoded qubits are easier to handle in quantum optics compared to qubits encoded as a superposition of two energy levels. In addition to the Mach-Zehnder interferometer 2, parallel paths 19 may also be realized as part of the integrated photonic chip 16 (not shown).

[0063] Figure 3 shows an experimental setup for manipulating a single photon, incorporating and using the quantum optical memristor 1 shown in Figure 2. A collinear type II SPDC source emits identical pairs of photons at 1550 nm. The source is based on a 30 mm PPKTP crystal 24 with a polling period of 46.2 μm adapted for downconversion from 775 to 1550 nm. The crystal is pumped by a CW-amplified diode laser 25 (Toptica TA Pro 780) with a pump power of approximately 80 mW. The crystal is inserted into a Sanyak interferometer 26 that generates photons with polarization entanglement, although in this particular case, entanglement is not used.

[0064] The optical components used to generate photons are labeled as follows: m...Mirror dm... Dichroic mirror QWP…Quarter wave plate HWP…half wave plate PBS...Polarizing Beam Splitter PPKTB...PPKTB crystal 24 Logical operation (logic)...Logical operation device

[0065] One of the photons, called the idler, is sent directly to the detector 27 for preparatory purposes, while the other of the photons, called the signal, is connected to the integrated photonic chip 16 via a single-mode fiber 28 directly bonded to the surface of the photonic chip 16. In the photonic chip 16, the signal photon passes through a state preparation stage 29, which includes a Mach-Zehnder interferometer 2a with a delay 13a, and then through a quantum optical memristor 1, which includes a parallel path 19, thereby allowing manipulation of qubits encoded by the two rails or paths. Thus, a state tomography stage 35 is present, which includes a Mach-Zehnder interferometer 2b and a delay 13b. The state tomography stage 35 is used to demonstrate that the device preserves any of the initial quantum coherence. The controller 10 is connected by a pigtail to a single-mode fiber 30 attached to the detector. We use a superconducting nanowire single-photon detector 9, 27, 34 (PhotonSpot Inc.) with an average detection efficiency of over 95%. We use three detectors 27, 9, and 34, namely one for the idler photon 27, one for the signal n(t)9, and one for the output signal 34 of the quantum optical memristor 1.

[0066] After detectors 9, 27, and 34, the logic unit 31 analyzes the signals. Each time the idler and signal n(t) match, the generation of a rectangular voltage pulse is triggered in the signal channel. The resulting signal is schematically shown on oscilloscope 33a (lower pulse train). Similarly, each time the idler and signal match, a voltage pulse is triggered in the output channel (upper pulse train on oscilloscope 33a). Using a pump power of approximately 80 mW at the source, the maximum match rate in each channel is approximately 3 × 10⁻¹⁶ per second. 4 This is the count. Next, both channels are low-pass filtered using filter 32 with RC = 100 milliseconds. This has the effect of averaging the pulse train and providing a continuous voltage signal. Here, the voltage signal is proportional to the pulse rate and then to the number of photons. Thus, measuring the output voltage of RC filter 32 constitutes a measurement of the number of photons. Note that the time constant RC should be much smaller than the integration time T. Here, T = 10 seconds is used.

[0067] In this regard, the output signal proceeds to the oscilloscope 33b for final data logging, while the feedback signal proceeds to the controller 10, which then processes n(t) and R target The controller 10 calculates and updates the reflectance R(t) value of the quantum optical memristor 1. The controller 10 changes the reflectance R(t) value by changing the voltage applied to the thermal phase shifter of the Mach-Zehnder interferometer 2. The phase shifter generates a phase shift proportional to the power consumed.

[0068] Figure 4 shows the experimental results (points) and simulation (line) obtained from the experimental setup shown in Figure 3. in n is the signal at the input, out This is the output signal. Oscillation period T osc It remains constant for 10 seconds, and the integral time T is equal to one oscillation period T. oscIt is modified within the range. The device does not approach the origin and exhibits a hysteresis diagram that is linear at high frequencies and nonlinear at low frequencies. The limit of high frequencies in this case is T=T osc Since it is the same, the experimental results provide a complete characterization of the device's dynamic response. The experimental data agree well with the simulated dynamics. Specifically, the low frequency limit n out =n in -n in 2 and the high frequency limit n out = 0.5 * n in This is as expected. This also aligns with the original definition of a memoristic device.

Claims

1. A quantum optical memristor (1) for manipulating photon quantum states, - A Mach-Zehnder interferometer (2) having at least a first optical input (3) and a first optical output (5) and a second optical output (6), - A detector (9) configured to detect the time-dependent optical signal n(t) at the second optical output (6) of the Mach-Zehnder interferometer (2), - Target reflectance R of the above Mach-Zehnder interferometer (2) ｔａｒｇｅｔ A controller (10) configured to calculate the following: The first optical input (3) and first optical output (5) of the above-mentioned Mach-Zehnder interferometer (2) are the first optical input (7) and first optical output (8) of the above-mentioned quantum optical memristor (1), respectively. The controller (10) above uses the calculated target reflectance R ｔａｒｇｅｔ The reflectance R(t) of the Mach-Zehnder interferometer (2) is configured to update to match the above, The above quantum optical memristor (1) is, The above controller (10) is the derivative of the reflectance with respect to time [Math 1] Based on the above target reflectance R ｔａｒｇｅｔ It is configured to calculate, The derivative of the above reflectance with respect to time [Math 2] This is a function of the detected signal n(t), The above function is characterized by including a negative term. Quantum optical memristor (1).

2. The above function is characterized by being a linear function of the detected signal n(t). The quantum optical memristor (1) according to claim 1.

3. The negative term described above is characterized by being a negative offset proportional to the maximum expected value of the signal n(t). The quantum optical memristor (1) according to claim 2.

4. The above controller (10) is the derivative of the reflectance [Math 3] Perform an integration step on the target reflectance R. ｔａｒｇｅｔ A configuration that is configured to acquire A quantum optical memristor (1) according to any one of claims 1 to 3.

5. The controller (10) performs a time window integration step over a time frame of length T to obtain the target reflectance R. ｔａｒｇｅｔ A configuration that is configured to acquire The quantum optical memristor (1) according to claim 4.

6. The length T of the above time frame is configurable, The quantum optical memristor (1) according to claim 5.

7. The length T of the time frame is configured to be less than or equal to the modulation period of the optical input signal at the optical input of the Mach-Zehnder interferometer (2), The quantum optical memristor (1) according to claim 6.

8. The signal n(t) in the above detector (9) is characterized in that it is related to the number of photons detected. The quantum optical memristor (1) according to claim 1.

9. A parallel path (19) having an optical input (20) and an optical output (21) is provided. The optical input (20) and optical output (21) of the above parallel path (19) are the second optical input (22) and second optical output (23) of the quantum optical memristor (1), respectively. The above parallel paths and the Mach-Zehnder interferometer (2) are configured to receive power from the same photon source. The above-mentioned parallel path (19) is characterized in that it does not essentially manipulate the state of photons in the above-mentioned parallel path (19). The quantum optical memristor (1) according to claim 1.

10. The parallel paths (19) are configured to relate to a first spatial mode, the Mach-Zehnder interferometer (2) is configured to relate to a second spatial mode of the qubit, and the qubit is encoded as a single photon which is a superposition of the first and second spatial modes. The quantum optical memristor (1) according to claim 9.

11. The above-mentioned Mach-Zehnder interferometer (2) is equipped with two beam splitters (14, 15), The above beam splitters (14, 15) are characterized by having a 50 / 50 splitting ratio. The quantum optical memristor (1) according to claim 1.

12. The above quantum optical memristor (1) is provided at least partially as part of an integrated photonic chip (16), At least the Mach-Zehnder interferometer (2) is characterized in that it is part of the integrated photonic chip (16). The quantum optical memristor (1) according to claim 1 or 11.

13. The above quantum optical memristor (1) is provided at least partially as part of an integrated photonic chip (16), At least the Mach-Zehnder interferometer (2) and the parallel path (19) are characterized in that they are part of the integrated photonic chip (16). The quantum optical memristor (1) according to claim 9 or 10.

14. The above quantum optical memristor (1) is at least partially based on glass, and the glass is laser-written, At least the above-mentioned Mach-Zehnder interferometer (2) is based on glass and is characterized by being laser-written onto the glass. The quantum optical memristor (1) according to claim 12.

15. The quantum optical memristor (1) is at least partially based on glass, and the glass is laser-written, At least the above-mentioned Mach-Zehnder interferometer (2) is based on glass and is characterized by being laser-written onto the glass. The quantum optical memristor (1) according to claim 13.

16. The above quantum optical memristor (1) is at least partially based on glass, and the glass is laser-written, At least the Mach-Zehnder interferometer (2) and the parallel path (19) are based on glass and are characterized by being laser-written onto the glass. The quantum optical memristor (1) according to claim 13.

17. The above-mentioned Mach-Zehnder interferometer (2) is equipped with two beam splitters (14, 15), The beam splitters (14, 15) are characterized by being guided directional couplers (17, 18). The quantum optical memristor (1) according to claim 1 or 11.

18. A method for manipulating optical qubits using a quantum optical memristor (1), The above quantum optical memristor (1) is, - A Mach-Zehnder interferometer (2) having at least a first optical input (3), a first optical output (5), and a second optical output (6), - A detector (9) configured to detect the time-dependent optical signal n(t) at the second optical output (6) of the Mach-Zehnder interferometer (2), - Target reflectance R of the above Mach-Zehnder interferometer (2) ｔａｒｇｅｔ A controller (10) configured to calculate the following: The first optical input (3) and first optical output (5) of the above-mentioned Mach-Zehnder interferometer (2) are the first optical input (7) and first optical output (8) of the above-mentioned quantum optical memristor (1), respectively. The controller (10) above uses the calculated target reflectance R ｔａｒｇｅｔ The reflectance R(t) of the Mach-Zehnder interferometer (2) is configured to update to match the above, The above method, - A step of supplying one or more photons to the quantum optical memristor (1) at the first optical input (7) of the quantum optical memristor (1), - A step of measuring the optical signal n(t) in the detector (9) above, - The target reflectance R calculated above ｔａｒｇｅｔ The steps include updating the reflectance R(t) of the Mach-Zehnder interferometer (2) to match the above, The above target reflectance R ｔａｒｇｅｔ is the derivative of the above reflectance with respect to time [Math 4] Calculated based on, The above reflectance [Math 5] This is a function of the detected signal n(t), The above function is characterized by including a negative term. method.

19. The quantum optical memristor (1) described above includes parallel paths (19) having an optical input (20) and an optical output (21), The optical input (20) and optical output (21) of the above parallel path (19) are the second optical input (22) and second optical output (23) of the quantum optical memristor (1), respectively. The first optical input (7) and the second optical input (22) of the quantum optical memristor (1) are configured to receive power from the same photon source. The above parallel path (19) essentially does not manipulate the state of photons in the above parallel path (19), The above parallel path (19) is configured to relate to a first spatial mode, the Mach-Zehnder interferometer (2) is configured to relate to a second spatial mode of the qubit, and the qubit is encoded as a single photon which is a superposition of the first and second spatial modes. The above method, - A qubit encoded as a photon, which is a superposition of the first and second spatial modes described above, is supplied to the quantum optical memristor (1). The method according to claim 18.

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