Method and system for providing electrical energy to cooling stage of cryostat system

Abstract

To provide electrical energy to an electronic circuitry.SOLUTION: The present invention relates to a method for providing electrical energy to an electronic circuitry. The electronic circuitry is located in a first cooling stage of a cryostat system operated at a first cooling temperature lower than 273 K. The method comprises the steps of: generating and emitting powering electromagnetic radiation outside the first cooling stage; illuminating a photovoltaic power converter with the powering electromagnetic radiation, where the photovoltaic power converter is located in the first cooling stage and the electronic circuitry is electrically connected to the photovoltaic power converter; generating electric current in the photovoltaic power converter; and electrically powering or biasing the electronic circuitry. In order to address the object, the method further comprises a step of transmitting excess energy introduced into the first cooling stage by the powering electromagnetic radiation out of the first cooling stage by means of at least dissipating electromagnetic radiation, the electric current, or heat transfer driven by the electric current.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method of supplying electrical energy to at least electronic circuitry located in a first cooling stage of a cryostat system operated at a first cooling temperature below 273 K. The method includes generating powering electromagnetic radiation at a location external to the first cooling stage, irradiating a photovoltaic power converter with the powering electromagnetic radiation, the photovoltaic power converter being located in the first cooling stage and having an electronic circuitry electrically connected to the photovoltaic power converter, generating a current in the photovoltaic power converter, and electrically powering or biasing the electronic circuitry.

[0002] The present invention also relates to a cryostat system comprising a first cooling stage operating at a first cooling temperature below 273 K, electronic circuitry, a photovoltaic power converter disposed in the first cooling stage, and a radiation source disposed external to the first cooling stage, the radiation source being positioned and arranged such that powering electromagnetic radiation is emitted by the radiation source to irradiate the photovoltaic power converter during use of the cryostat system, and the electronic circuitry is electrically connected to the photovoltaic power converter such that the photovoltaic power converter electrically powers or biases the electronic circuitry during operation of the cryostat system. [Background technology]

[0003] Cryogenic applications of electronic circuits typically require conductive wiring, which requires a feed-through interface in the cryostat's thermal insulation structure, impairing the cryostat's thermal insulation efficiency. When metal wires are used in existing applications, heat is transferred to the cryostat system's cooling stage or stages, which may operate at temperatures as low as several degrees Kelvin. Heat is transferred from ambient (room temperature) conditions to the cryostat. Heat conduction has proven particularly problematic with coaxial cables. This is because the electrical insulation of the center conductor also acts as a thermal insulator, allowing heat to be efficiently transferred from the ambient environment through the center conductor to the cooling stage. Such coaxial electrical wires require the use of attenuators, e.g., 0 dB, in each cooling stage to thermally match the conductors, which increases the complexity of the cryostat system. This reduces the overall efficiency of the cryostat system and forces the use of large, powerful cryogenic refrigerators, which increases cost and complexity.

[0004] This becomes especially important in cryogenic systems, for example in quantum computers, where the number of electronic and optoelectronic elements in the cooling stage is scaled up. As the number of electronic and optoelectronic elements in the cooling stage increases, so does the number of interfaces providing either power, bias, or signaling. In such cases, the minimum cooling power required for a cryostat system becomes determined by the number of interfaces, not the low temperatures the system is to reach.

[0005] Thus, the prior art reports methods for supplying electrical energy to the electronic circuits in a cryostat, in which the energy is transferred from the ambient environment to the cooling stage by photons rather than by conductive wires. Summary of the Invention [Problem to be solved by the invention]

[0006] However, it has been found that depending on the application, i.e., the elements being powered or biased, excess energy may be introduced into each cooling stage, which, at least at a certain point in time, is not used by any of the elements in the cooling stage and reduces the cooling efficiency of the entire cryogenic system.

[0007] Therefore, there is a need for a method of providing electrical energy to electronic circuitry located in the first cooling stage of a cryostat system. Additionally, there is a need for a cryostat system that can more efficiently provide sub-ambient temperatures. [Means for solving the problem]

[0008] At least one of the above objects is solved by a method according to the invention as defined in independent claim 1. The method therefore further comprises the step of transmitting excess energy introduced into the first cooling stage by powering electromagnetic radiation out of the first cooling stage by at least dissipating electromagnetic radiation, electric current or heat transfer driven by electric current.

[0009] At least one of the above objects is also achieved by a cryostat system as set forth in independent claim 7. According to the invention, such a cryostat system comprises a transmitting element, which is electrically connected to or is a photovoltaic power converter, and which is arranged to transmit, during operation of the cryostat system, excess energy introduced into the first cooling stage by powering electromagnetic radiation out of the first cooling stage by dissipating electromagnetic radiation, by electric current or by heat transfer driven by electric current.

[0010] The basic idea of ​​the present invention is to transmit the excess energy introduced into the first cooling stage by the power supply electromagnetic radiation out of the first cooling stage using current generated by electromagnetic radiation, i.e. photons, or by a photovoltaic converter of the first cooling stage.

[0011] In one embodiment, excess electrical energy from multiple photovoltaic converters powering or biasing electronic circuits is dissipated by a single transmit element.

[0012] In one embodiment, excess electrical energy from a single photovoltaic converter powering or biasing an electronic circuit is dissipated by multiple transmit elements.

[0013] The transmission of energy to power or bias the electronic circuit according to the invention is carried out by generating powering electromagnetic radiation in a radiation source external to the first cooling stage. The generated electromagnetic radiation is then guided to the first cooling stage. This can be done through free space using a transparent window in the thermally insulating structure of the cryostat system or by fiber coupling. Fiber coupling is advantageous because it reduces the thermal load introduced into the system. Optical fiber has a much higher thermal resistance than conductive wires.

[0014] In one embodiment, the powering electromagnetic radiation is provided by an array of radiation sources, for example an array of vertical cavity surface emitting lasers, hi a further embodiment, the powering electromagnetic radiation originating from the multiple radiation sources in the array is coupled by optical guiding means into a single electromagnetic waveguide that directs the radiation to the photovoltaic converter or converters.

[0015] A photovoltaic converter (PVC) is a structure that converts electromagnetic radiation emitted from an artificial electromagnetic radiation source into electrical energy. The combination of an artificial electromagnetic radiation source and a photovoltaic converter is also referred to as a power-by-light system. A power-by-light system is used to provide energy to remote devices that are not connected to a power grid. In one embodiment, the photovoltaic converter is optimized for single- or multiple-narrow-band light energy delivery. In contrast, the solar cell structure is designed to provide high efficiency over as broad a spectrum as possible that matches the white electromagnetic spectrum of the sun. In a further embodiment, the electromagnetic radiation source of the power-by-light system is configured to emit powering electromagnetic radiation having a wavelength spectrum with a full width at half maximum of 100 nm or less, preferably 50 nm or less, 10 nm or less, or 5 nm or less. In one embodiment, the photovoltaic converter is optimized to generate an electric current when irradiated by powering electromagnetic radiation having a wavelength spectrum with a full width at half maximum of 100 nm or less, preferably 50 nm or less, 10 nm or less, or 5 nm or less.

[0016] Photovoltaic power converters are typically power sources. In contrast to photovoltaic power converters, photodiodes are designed to sense electromagnetic radiation by producing a photo-generated current. Photovoltaic power converters differ from photodiodes in their operation. Photovoltaic power converters operate in the fourth quadrant of the current-voltage relationship, while photodiodes typically operate in the third quadrant of the current-voltage relationship. The fourth quadrant of the current-voltage relationship is defined as the region with positive voltage and negative current, resulting in negative power. In the context of electronics, this refers to power generation from the device to an external circuit. The third quadrant of the current-voltage relationship is defined as the region with negative voltage and negative current, resulting in positive power. In the context of electronics, this refers to power consumption from the external circuit to the device.

[0017] Key parameters in optimizing PVC are the device output power and device power density. Higher output power allows for a wider range of applications for power-by-light systems, while higher power density allows for a smaller footprint, thereby facilitating device miniaturization and lower manufacturing costs. In one embodiment, the PVC includes a multi-junction structure. PVC with such stacked junctions is referred to as a multi-junction design, where the output voltage of a single junction is multiplied by the number of junctions in the stack.

[0018] In one embodiment, the system includes at least an array of photovoltaic converters or an array of transmit elements. The array may have 10 or more photovoltaic converters. In one embodiment, the array includes 100 or more photovoltaic converters, or 1,000 or more photovoltaic converters, or 10,000 or more photovoltaic converters. When the system includes an array of photovoltaic converters, each photovoltaic converter requires electronic circuitry and electrical connection to at least one transmit element.

[0019] A number of these arrays are used to power or bias electronic circuits, with some arrays differing in the configuration of the photovoltaic converter and optionally the transmit element.

[0020] In further embodiments, the array of at least a plurality of photovoltaic converters or the array of a plurality of transmitter elements are arranged as a single chip assembly. In further embodiments, the array of at least a plurality of photovoltaic converters or a plurality of transmitter elements are monolithically fabricated on a single chip. In further embodiments, the array is formed as a plurality of chip assemblies called chiplets.

[0021] In a further embodiment, the powering electromagnetic radiation is supplied to multiple photovoltaic converters by a single waveguide, and an optical combining element, such as a demultiplexer, is used to direct a portion of the powering electromagnetic radiation to each photovoltaic converter, In one embodiment, the demultiplexing is based on optical properties such as wavelength, polarization, phase, intensity, modulation frequency, slew rate, pulse width, etc.

[0022] In a further embodiment, a photonic integrated waveguide circuit routes powering electromagnetic radiation from a plurality of electromagnetic waveguides to a plurality of photovoltaic converters. In a further embodiment, the photonic integrated waveguide is based on silicon-on-insulator technology. In a further embodiment, the photonic integrated waveguide circuit includes signal separation elements for demultiplexing or splitting signals. In a further embodiment, the photonic integrated waveguide circuit includes light directing elements for splitting light from a single waveguide to a plurality of photovoltaic converters.

[0023] In one embodiment, light from multiple transmit elements is directed into a single electromagnetic waveguide, which directs the dissipated electromagnetic radiation to a higher cooling temperature or to an ambient temperature outside the cryogenic system.

[0024] In one embodiment, the array of photovoltaic converters or the array of transmitter elements is configured such that the electrical connections are located on opposite sides of the photovoltaic converter or transmitter element array assembly. In a further embodiment, vias connect the photovoltaic converter or transmitter element array to the electrical connections. In a further embodiment, a ball grid array method is used to achieve these electrical back-to-back connections.

[0025] Therefore, in one embodiment of the present invention, the cryostat system also includes a source of powered electromagnetic radiation, i.e., the system constitutes an overall power-by-write system. In one embodiment, the source of powered electromagnetic radiation is a laser, in particular a laser diode or a light-emitting diode.

[0026] According to a particular embodiment of the invention, the radiation source is not only external to the first cooling stage, but is also located in the ambient environment, outside the thermally insulating structure of the cryostat system.

[0027] In this application, the term "powering electromagnetic radiation" refers to electromagnetic radiation generated outside of and transmitted to the first cooling stage to illuminate the photovoltaic converter, whereas in this application, electromagnetic radiation that transmits excess energy from the first cooling stage to the outside is referred to as "dissipated electromagnetic radiation."

[0028] A cryostat system according to the invention comprises at least one cooling stage, referred to as the "first cooling stage", which is at a temperature below 273 K, i.e. well below room temperature.

[0029] In one embodiment of the present invention, the first cooling stage has a first cooling temperature of 175 K or less, preferably 77 K or less, or 15 K or less, or 10 K or less, or 4.5 K or less. In another embodiment, the first cooling stage has a first cooling temperature of 1.5 K or less. Typically, the superconducting electronic circuit is operable at 1.5 K.

[0030] In one embodiment of the present invention, the cryostat system comprises at least two of a plurality of cooling stages, namely a first cooling stage, a second cooling stage, and a third cooling stage, all of which are at temperatures well below room temperature, in particular the first cooling temperature, the second cooling temperature, and the third cooling temperature are below 273 K. In one embodiment, the second cooling stage has a second cooling temperature below 273 K and higher than the first cooling temperature.

[0031] In one embodiment of the present invention, the cryostat system includes a second cooling stage having a second cooling temperature, the second cooling temperature being lower than 273 K and higher than the first cooling temperature, the photovoltaic converter being disposed on the first cooling stage, and the transmitting element being disposed on the second cooling stage.

[0032] In one embodiment of the present invention, the cryostat system includes a second cooling stage having a second cooling temperature, the second cooling temperature being lower than 273 K and higher than the first cooling temperature, and the photovoltaic converter, the transmitting element, and the electronic circuitry are not located in the second cooling stage.

[0033] In a further embodiment, the cryostat system has a third cooling stage with a third cooling temperature, the third cooling temperature being lower than the first cooling temperature. In one embodiment, electronic circuitry is disposed on the third cooling stage. Optionally, the third cooling stage has a third cooling temperature of 1.5 K or less.

[0034] Thus, the first cooling temperature, the second cooling temperature, and the third cooling temperature are related to each other as follows: Third cooling temperature < First cooling temperature < Second cooling temperature < 273K However, a method and cryostat system according to the present invention having a third cooling stage at a third cooling temperature does not necessarily have to have a second cooling stage.

[0035] In one embodiment, the cryostat system includes a third cooling stage, where the electronic circuitry is located, and the transmitting element is located on the first cooling stage.

[0036] In a further embodiment, the electronic circuit is disposed in a third cooling stage having a third cooling temperature. The third cooling temperature is lower than the first cooling temperature. In one embodiment of the present invention, the cryostat system has a first cooling stage and a third cooling stage, with the photovoltaic power converter disposed in the first cooling stage and the electronic circuit disposed in the third cooling stage. In one embodiment, the cryostat system does not have a second cooling stage. Thus, the transmitting element is disposed in the first cooling stage. In a further embodiment, the cryostat system has a second cooling stage in addition to the first and third cooling stages. In such an embodiment, the transmitting element may be disposed in the second cooling stage.

[0037] In one embodiment, electrical wiring between the photovoltaic power converter of the first cooling stage and the electronic circuitry of the third cooling stage is provided by superconducting wires, electrical leads or conductors.

[0038] In further embodiments, the material of the superconducting wire, electrical lead, or conductor comprises a niobium-titanium alloy. In further embodiments, the first cooling temperature is 10 K or less below the critical temperature of the material comprising the niobium-titanium alloy. In further embodiments, the second cooling temperature is 5 K or less or 3 K or less.

[0039] In a further embodiment, the material of the superconducting wire, electrical lead or conductor comprises aluminum or an alloy with an aluminum content of 5% or more, hi a further embodiment, the first cooling temperature is 1.5 K or less below the critical temperature of the material containing aluminum or an alloy including aluminum.

[0040] In further embodiments, the material of the superconducting wire, electrical lead or conductor comprises niobium, niobium nitride (NbN), niobium titanium (NbTi), niobium tin (NbSn), phosphor bronze, yttrium barium copper oxide (YBCO), lead (Pb), or an alloy containing 5% or more of any of these materials.

[0041] In one embodiment, the multiple cooling stages of the cryostat system are arranged in series.

[0042] In one embodiment of the present invention, the step of transmitting the excess energy includes generating dissipated electromagnetic radiation in a light-emitting element driven by current generated by the photovoltaic converter, and transmitting the dissipated electromagnetic radiation to a location external to the first cooling stage. Thus, in one embodiment of the cryostat system, the transmitting element is a light-emitting element that converts current into dissipated electromagnetic radiation during operation of the cryostat system. Preferably, the light-emitting element is a laser diode or a light-emitting diode (LED).

[0043] The transmitting element of a cryostat system according to an embodiment of the present invention is arranged to transmit excess energy as radiated electromagnetic radiation during operation of the cryostat system, the cryostat system comprising means for directing the radiated electromagnetic radiation out of the first cooling stage.

[0044] This means is, for example, a window or an electromagnetic waveguide for the radiated electromagnetic radiation (for example an optical fiber).

[0045] In a further embodiment, the radiated electromagnetic radiation from the multiple transmitting elements is transmitted through a single waveguide. The radiated electromagnetic radiation is directed to multiple receivers via an optical combining element, such as a multiplexer. The optical combining element is used to direct the radiated electromagnetic radiation to the multiple receivers. In one embodiment, the multiplexing is based on optical properties such as wavelength, polarization, phase, intensity, modulation frequency, slew rate, pulse width, etc.

[0046] In a further embodiment, the photonic integrated waveguide circuit routes the dissipated electromagnetic radiation from each transmit element into multiple electromagnetic waveguides. In a further embodiment, the photonic integrated waveguide is based on silicon-on-insulator, silicon nitride, lithium niobate, or lithium tantalate technology. In a further embodiment, the photonic integrated waveguide circuit includes an optical splitting element, such as a demultiplexer.

[0047] In one embodiment, light from multiple transmit elements is directed into a single electromagnetic waveguide, which directs the dissipated electromagnetic radiation to a higher cooling temperature or to ambient temperature outside the cryogenic system.

[0048] In one embodiment of the invention, at least the photovoltaic converter or the light emitting element are coupled to an electromagnetic waveguide, for example, an optical fiber. In one embodiment, the photovoltaic converter is coupled by an electromagnetic waveguide and the light emitting element is coupled by another electromagnetic waveguide.

[0049] In one embodiment of the present invention, the photovoltaic converter and the light emitting element are coupled to a single electromagnetic waveguide, in particular a single optical fiber.

[0050] In this embodiment, the cryostat system comprises a light emitting element, for example a semiconductor laser, a laser diode or a light emitting diode, for generating photons that carry excess energy from the first cooling stage.

[0051] In one embodiment of the present invention, the light emitting element is located in a first cooling stage. However, embodiments are also possible in which the light emitting element is located in a cryostat but outside of the first cooling stage. In one embodiment, the light emitting element is located in a second cooling stage. The second cooling stage is at a second cooling temperature, which is higher than the first cooling temperature.

[0052] In this application, the terms first, second, and third cooling stages are used to distinguish between different cooling stages, without indicating a particular order of these cooling stages. The numerals first, second, and third are used to distinguish between cooling stages at different temperature levels, without requiring the implementation of all cooling stages, unless otherwise specified in the claims. A cryostat system may have multiple cooling stages, particularly more than three cooling stages.

[0053] In one embodiment of the cryostat system, the photovoltaic power converter includes a plurality of active junctions, and the output voltage of the photovoltaic power converter is at least equal to or greater than the threshold voltage of the light emitting element.

[0054] In one embodiment of the cryostat system, the photovoltaic power converter has a PVC junction operating point voltage, and the light-emitting device has an emitter threshold voltage that is equal to or less than the operating point voltage. By satisfying this condition, the combination of the photovoltaic power converter and the light-emitting device can be designed so that the photovoltaic power converter generates a voltage sufficient to power the light-emitting device.

[0055] In one embodiment of the cryostat system of the present invention, the photovoltaic converter includes a converter bandgap and a plurality of PVC junctions, and the light-emitting device has an emitter threshold voltage that is less than the sum of the operating point voltages of the plurality of PVC junctions. By satisfying this condition, the combination of the photovoltaic converter and the light-emitting device can be designed so that the photovoltaic converter generates a voltage sufficient to power the light-emitting device.

[0056] In a further embodiment of the cryostat system, the light-emitting element is connected in series or parallel to the electronic circuit. A series connection of light-emitting elements is particularly advantageous in superconducting electronic circuits. During operation, the light-emitting element transmits dissipated electromagnetic radiation while in a superconducting state (low series resistance) and is switched off while the superconducting electronic circuit is in a resistive state (high series resistance). The advantage of a series connection used with a superconducting electronic circuit is that it can effectively transmit excess energy from the first cooling stage by transmitting dissipated electromagnetic radiation. The advantage of a series connection is further enhanced when the superconducting electronic circuit remains in a superconducting state for the majority of the operating time and quickly recovers from a resistive state to a superconducting state. In a parallel connection, where the superconducting electronic circuit acts as a shunt resistor, the light-emitting element operates while the superconducting element is in a resistive state. In the context of a superconducting electronic circuit, a parallel connection is preferable when the superconducting electronic circuit is in a resistive state for the majority of the operating cycle and only temporarily switches to the superconducting state.

[0057] In one embodiment of the present invention, the photovoltaic converter and the light emitting element are implemented as separate devices, i.e., two different chip assemblies. However, in an alternative embodiment of the present invention, the photovoltaic converter and the light emitting element are integrated into a single optoelectronic chip assembly.

[0058] Instead of generating photons that transfer excess energy outside the first cooling stage, the current is used to generate heat outside the first cooling stage or to power a heat transfer process that transfers excess energy away from the first cooling stage, thereby cooling the first cooling stage and heating a heat sink external to the first cooling stage.

[0059] Thus, in a further embodiment, transmitting the excess energy comprises conducting an electric current through an electrical resistor located external to the first cooling stage, which converts the excess current, and therefore excess power, into heat.

[0060] In yet another embodiment, transmitting the excess energy includes powering a solid-state heat pump with an electric current, the solid-state heat pump having a cold side disposed in a first cooling stage and a hot side disposed outside the first cooling stage at a temperature higher than the first cooling temperature. In such an embodiment, the transmitting element is a solid-state heat pump. In one embodiment, the hot side of the solid-state heat pump is located in a second cooling stage. In one embodiment, the solid-state heat pump is a Peltier element.

[0061] In one embodiment, the excess energy directed out of the first cooling stage is used to power other elements of the cryostat system external to the first cooling stage. Alternatively or additionally, the excess energy directed out of the first cooling stage is fed back to the photovoltaic converter as powering electromagnetic radiation. These embodiments promote energy-efficient operation of the entire cryostat system.

[0062] In one embodiment, at least a portion of the excess energy is temporarily fed into an energy storage device located in the cooling stage of the cryostat system and stored for later use.

[0063] In one embodiment of the cryostat system, the transmitting element is disposed to convert electrical energy into heat during operation of the cryostat system and is located external to the first cooling stage. In one embodiment, the energy transmitting element is an electrical resistor. In an embodiment, the electrical resistor does not emit light. In an embodiment, the electrical resistor is of a variable load type.

[0064] By locating the electrical resistor external to the first cooling stage, the power dissipated by the electrical resistor is not included in the heat load of the first cooling stage. In one embodiment of the invention, the electrical resistor is located in the second cooling stage. Optionally, the electrical resistor is not a photon-generating optoelectronic device, and in particular does not intentionally generate radiative electromagnetic radiation.

[0065] In one embodiment, the device includes a first cooling stage and a third cooling stage having a third cooling temperature, the third cooling temperature being lower than the first cooling temperature, and no second cooling stage is provided. In this embodiment, the electrical resistor may be disposed in the first cooling stage.

[0066] In the above embodiment, the radiated electromagnetic radiation is generated by a light-emitting element and then emitted outside the first cooling stage, where the current generated by the photovoltaic converter drives the light-emitting element.

[0067] However, other possibilities for transmitting excess energy by photons are also conceivable, and therefore, according to a further embodiment of the invention, the step of transmitting excess energy comprises radiating dissipated electromagnetic radiation from the photovoltaic converter to a predetermined location outside the first cooling stage.

[0068] In one embodiment of the present invention, a photovoltaic power converter is the transmitting element, and the photovoltaic power converter is positioned to emit radiated electromagnetic radiation to a location outside the first cooling stage during operation of the cryostat system.

[0069] In this embodiment, in the case where the dissipated electromagnetic radiation is emitted from the photovoltaic converter itself, the radiation may be based on the following two methods or a combination thereof: In one embodiment, the power supply electromagnetic radiation irradiating the photovoltaic converter is reflected by the photovoltaic converter insofar as it is excess radiation that cannot contribute to power generation. In one embodiment, the photovoltaic converter comprises a reflector, which is arranged behind the active layer of the photovoltaic converter in the transmission direction of the incident power supply electromagnetic radiation. Only light that is not absorbed by the photovoltaic converter is reflected. In situations where the photovoltaic converter absorbs more power supply electromagnetic radiation, less electromagnetic radiation is reflected out of the first cooling stage, and vice versa. In these embodiments, the reflected electromagnetic radiation is referred to as radiated electromagnetic radiation. In another embodiment, the radiated electromagnetic radiation is generated in the photovoltaic converter due to absorption of the power supply electromagnetic radiation and re-emission of photons of the radiated electromagnetic radiation from the photovoltaic converter.

[0070] In an embodiment of the invention, the dissipated electromagnetic radiation or current at a location external to the first cooling stage is used not only to transmit excess energy outside the first cooling stage, but also to signal the state of the electronic circuitry. Thus, in one embodiment of the invention, a method includes detecting the dissipated electromagnetic radiation or current at a location external to the first cooling stage, generating a detector signal representative of a characteristic of the dissipated electromagnetic radiation or current, and determining the state of the electronic circuitry from the detector signal.

[0071] In a further embodiment of the invention, the radiated electromagnetic radiation or current at a location external to the first cooling stage is used not only to transmit excess energy outside the first cooling stage, but also to signal the state of the cryostat system, which in this embodiment changes at least one characteristic of the radiated electromagnetic radiation or current transmitted from the transmitting element.

[0072] In one embodiment, the photovoltaic converter and the transmitting element are impedance matched to the electronic circuit. In a further embodiment, radiated electromagnetic radiation is used for signal transmission and the photovoltaic converter and the transmitting element are impedance matched to the electronic circuit. Impedance matching reduces signal reflections or maximizes the transmitted signal, at least at high frequency operation.

[0073] The property of the emitted electromagnetic radiation that determines the state of the electronic circuit or that determines the state of the cryostat system is selected from the group consisting of wavelength, polarization, slew rate, phase, pulse width, modulation frequency and intensity, or a combination thereof.

[0074] In one embodiment of the cryostat system, the cryostat system includes a detector and a controller located external to the first cooling stage. The controller is operatively connected to the detector to receive a detector signal from the detector during operation of the cryostat system. The detector signal is representative of a characteristic of the radiated electromagnetic radiation detected by the detector. The detector is positioned and arranged to detect the radiated electromagnetic radiation emitted from the light-emitting element during operation of the cryostat system. The controller is configured to determine a state of the electronic circuitry from the detector signal.

[0075] In one embodiment, the cryostat system includes a receiver located and arranged to receive the radiated electromagnetic radiation emitted by the light-emitting element during operation of the cryostat system. The energy obtained by the receiver can be used to power any type of electronic device, reusing excess energy transmitted from the first cooling stage. In one embodiment, the receiver is a photovoltaic converter or a photodiode.

[0076] In one embodiment of the invention, the electronic circuit includes or is at least a sensor, a cooling device or an actuator, hi one embodiment, the cooling device is a thermoelectric cooler.

[0077] In a further embodiment of the invention, the sensor comprises or is a superconducting sensor and the actuator is a superconducting actuator.In a preferred embodiment, the superconducting sensor is a superconducting nanowire single photon detector (SNSPD).

[0078] In one embodiment of the present invention, the electronic circuit comprises a field effect transistor, such as a high electron mobility transistor, a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a junctionless nanowire transistor, a metal-nitride-oxide-semiconductor transistor, an ion-sensitive field effect transistor, a junction field effect transistor, an epitaxial diode field effect transistor with fast reverse operation or fast recovery, a heterostructure insulated gate field effect transistor, a tunnel field effect transistor, a metal-semiconductor field effect transistor, a nanoparticle organic memory field effect transistor, a graphene nanoribbon field effect transistor, a vertical slit field effect transistor, a carbon nanotube field effect transistor, a quantum field effect transistor, a Schottky barrier field effect transistor or a vertical transport field effect transistor.

[0079] In one embodiment of the present invention, the electronic circuit includes an amplifier such as a traveling wave parametric amplifier, a Josephson traveling wave parametric amplifier, a Josephson junction amplifier, a high electron mobility transistor amplifier, or a high electron mobility transistor low noise amplifier.

[0080] In one embodiment of the present invention, the electronic circuit includes a signal generator, such as a Josephson junction arbitrary waveform synthesizer.

[0081] In one embodiment of the present invention, the electronic circuit includes qubits based on trapped ion qubits, neutral atom qubits, superconducting qubits, quantum dot qubits, spin defect qubits, topological qubits, or photonic qubits.

[0082] In one embodiment of the present invention, the electronic circuit comprises a magnet, a transformer, a calorimeter such as a bolometer, a single flux quantum, a superconducting quantum interference device, or a superconductor-semiconductor topological Josephson junction.

[0083] In further embodiments, at least a portion of the electronic circuitry is fabricated using complementary metal-oxide-semiconductor technology, silicon-on-insulator technology, photonic integrated circuit technology, III-V-on-silicon technology, silicon technology and III-V technology, or a combination of these technologies.

[0084] In a further embodiment of the invention, the electronic circuit is part of a quantum computer.

[0085] In one embodiment, the electronic circuitry includes a solid-state cooling device, for example a thermoelectric cooling device such as a Peltier element.

[0086] Further advantages, features and applications of the present invention will become apparent from the following description of the embodiments and the corresponding accompanying drawings. The foregoing description and the following detailed description of the embodiments can be more fully understood by reading them in conjunction with the accompanying drawings. It should be understood that the illustrated embodiments are not limited to the precise arrangements and equipment shown. In the drawings, identical components are designated by identical reference numerals. [Brief explanation of the drawings]

[0087] [Figure 1] FIG. 1 is a schematic diagram of a prior art cryostat system. [Figure 2] FIG. 2 is a schematic diagram of a cryostat system according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram of a cryostat system according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram of a cryostat system according to a third embodiment of the present invention. [Figure 5] FIG. 5 is a schematic diagram of a cryostat system according to a further embodiment of the present invention. [Figure 6] FIG. 6 is a schematic diagram of an array configuration of multiple photovoltaic converters and multiple transmit elements. [Figure 7] FIG. 7 is a schematic diagram of a cryostat system according to another embodiment of the present invention. [Figure 8] FIG. 8 is a schematic diagram of a cryostat system according to yet another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0088] The basic concept of the present invention will be explained with reference to the figures, assuming that a superconducting nanowire single-photon detector (SNSPD) 2 is powered and readout. The SNSPD 2 forms an example of an electronic circuit according to the present invention. To exhibit its superconducting properties, the SNSPD 2 must be cooled to an operating temperature selected based on the superconducting material of the SNSPD 2, so that the detector is maintained well below its critical temperature. The SNSPD 2 is therefore part of a cryostat system 1. In the illustrated example, the SNSPD 2 is arranged in a cryostat constituting a first cooling stage 3 with a first cooling temperature of 3.5 K.

[0089] SNSPD2 in Figures 1, 2 and 4 has a kinetic inductance L k , hot spot resistance R nThe cryostat is represented by an equivalent circuit consisting of a switch 5 that simulates the state in which a photon is absorbed and a resistor 6 that detects the photon absorption. The open and closed states of the switch 5 correspond to the resistive state (when a photon is absorbed) and the superconducting state (when no photon is absorbed), respectively. In the prior art, as shown schematically in Figure 1, the interface for external biasing and readout consists of an external DC current source 6 and a load impedance 7 located outside the cryostat 8. Such electrical biasing and readout requires an RF cable pair 9 for each detector channel. The copper cables of the cable pair must be thermally connected to each of the first and second cooling stages 3 and 4, for example, by a 0 dB attenuator. This is to avoid direct thermal contact between the first and second cooling stages 3 and 4 and the ambient environment 10 via the cable pair 9. This increases the complexity of the cryostat system in proportion to the number of SNSPDs 2 required for a particular application. It should also be noted that the heat load leaking from room temperature to the cold stages increases as the number of SNSPDs 2 increases, regardless of the level of Joule heating in the first cooling stage.

[0090] In the example described with reference to the figures, the photons detected by the SNSPD 2 are generated in another element in the cryogenic environment, for example the first cooling stage.

[0091] The SNSPD 2 applied to the prior art design described above with reference to FIG. 1 and the SNSPD 2 applied to the embodiments of the present invention shown in FIGS. 2-4 are both known in the prior art. The operation of an SNSPD 2 can be summarized as follows: The SNSPD 2 is biased with a DC current close to the critical current that causes quenching to the resistive state. Absorption of a single photon creates a small resistive hot spot. Due to the small cross-sectional area of ​​the nanowire, the local current density of the supercurrent exceeds a critical value. As a result, a resistive barrier forms across the entire cross-section of the nanowire. Resistive heating causes the resistive barrier to grow along the axial direction of the nanowire. In the prior art, at this point the bias current is diverted by external readout circuitry 6, 7, allowing the nanowire to restore its superconducting state.

[0092] 2 to 4, according to the present invention, in order to avoid direct thermal contact between the first and second cooling stages 3, 4 and the ambient environment 10, the external biases 6, 7 and the pair of interface cables 9 are replaced by a laser 11 as a light-emitting element in the ambient environment 10 and a photovoltaic converter (PVC) D1 in the first cooling stage 3. The laser 11 and the photovoltaic converter D1 are coupled by a waveguide for electromagnetic radiation, i.e., an optical fiber 13. The laser radiation emitted by the laser 11 and introduced into the optical fiber 13 supplies a supercurrent through the SNSPD 2 and thus power to the SNSPD 2, and is therefore referred to as power electromagnetic radiation.

[0093] The use of PVC D1 dramatically reduced the heat losses in the first cooling stage 3 and the second cooling stage 4 caused by the prior art cable pair 9. In contrast to conductive wires, optical fibers have a much higher thermal resistance.

[0094] The embodiment of Figure 2 is optimized for powering SNSPDs 2, which require a controllable bias current and do not require high voltages, but which have near-zero resistance in the superconducting state.

[0095] In the embodiment of Figure 2, an external load is used to maximize the conversion efficiency of the PVC D1. This load is a light-emitting diode (LED), designated D2 in Figure 2. The optical power generated and emitted by the LED D2 is transmitted to the ambient environment 10 using an optical fiber 14. For this reason, the LED D2 is also referred to as a transmitting element in this application. The electromagnetic radiation generated by the LED D2 is referred to as dissipated electromagnetic radiation because it dissipates the heat load from the first cooling stage 3. A portion of the excess energy transported by the powering electromagnetic radiation to the first cooling stage 3 is rejected from the cryostat 8 as light and is not converted to heat.

[0096] The LED D2 and the PVC D1 are connected in series. Therefore, the intensity of the radiated electromagnetic radiation emitted by the LED D2 reflects the state of the PVC D1 device. The intensity of the radiated electromagnetic radiation emitted by the LED D2 depends on the operating current and voltage of the PVC D1. Because the SNSPD2 is in the same circuit as the LED D2 and the PVC D1, the state of the SNSPD2 is also reflected in the intensity of the radiated electromagnetic radiation emitted by the LED D2.

[0097] Thus, the dissipated electromagnetic radiation emitted by the LED D2 and guided through the optical fiber 14 is detected in the surrounding environment 10 by the photodiode 15. The intensity detected by the photodiode 15 indicates the state of the SNSPD 2 and thus the measurement result of the SNSPD 2.

[0098] 4, in the embodiment of FIG. 2, all components can and are located in the first cooling stage 3, which is at the lowest cooling temperature of the cryostat system 1. This allows for easy and scalable system-level integration. The second cooling stage 4 is empty in the sense that it does not contain any of the photovoltaic converter D1, light-emitting diode D2, or SNSPD2.

[0099] The PVC D1 in the described embodiment is a multi-junction structure capable of generating the threshold voltage required to power the LED D2 in the embodiments according to Figures 2 and 5. To lower the threshold voltage of the LED D2, the bandgap of the LED D2 is smaller than the bandgap of the PVC D1. In the described embodiment, the junction of the PVC D1 is a GaInP junction and the LED D2 is based on GaAs. In a further embodiment, the junction of the PVC D1 is a GaAs junction and the LED D2 is based on GaInAs.

[0100] In the embodiment of Figure 3, excess energy introduced into the first cooling stage is also transferred from the first cooling stage to the outside by electromagnetic radiation. However, the embodiment of Figure 3 relies on the function of the PVC D1 itself rather than a separate LED D2. In Figure 3, instead of showing a complete equivalent circuit, the SNSPD2 is depicted schematically. As mentioned above, the PVC D1 operates near a short-circuit condition and therefore functions as a photocurrent generator.

[0101] The powering electromagnetic radiation irradiating the PVC D1 is reflected by a reflective layer that is part of the PVC D1. In the beam direction of the powering electromagnetic radiation, the reflective layer is arranged behind the active layer of the PVC D1. Thus, the powering electromagnetic radiation that has not been absorbed by the active layer is reflected. After reflection, this radiation becomes radiated electromagnetic radiation and is coupled into the fiber 13. Thus, the fiber 13 serves as a fiber for the powering electromagnetic radiation and the radiated electromagnetic radiation.

[0102] In the exemplary embodiment of FIG. 4, a heat sink resistor R in the second cooling stage 4 is used to transfer excess power from the first cooling stage 3. L This heat sink resistor R L replaces LED D2 in the embodiment of FIG. 2 and is a transmitting element in the sense of the present application.

[0103] Heat dissipation resistor R LWhen is properly selected or controlled, the power conversion efficiency of the PVC D1 is maximized, thereby minimizing heat loss in the first cooling stage 3. Most of the heat loss is transmitted to the second cooling stage 4. Therefore, using this approach, the heat load on the first cooling stage 3 is reduced by 50% to 70%, and the excess energy is transmitted to the second cooling stage 4 to be dissipated remotely.

[0104] In the exemplary embodiment of Fig. 7, a Peltier element 23, which is an example of a solid-state heat pump, is used to extract excess power from the first cooling stage 3. The Peltier element 23 is disposed at the boundary between the first cooling stage 3 and the second cooling stage 4, with a low-temperature side 24 of the Peltier element 23 located in the first cooling stage 3 and a high-temperature side 25 located in the second cooling stage 4. The Peltier element 23 is similar to the LED D2 in the embodiment of Fig. 2 or the heat sink resistor R in the embodiment of Fig. 4. L The Peltier element 23 is the transmitting element in this embodiment.

[0105] When the Peltier element 23 is properly selected or controlled, the power conversion efficiency of the PVC D1 is maximized, thereby minimizing heat loss in the first cooling stage 3. Most of the heat loss is transmitted by the Peltier element 23 to the second cooling stage 4.

[0106] The cryostat system 1 of FIG. 5 is very similar in design to the system 1 of FIG. 2. However, instead of two cooling stages as in FIG. 2, the cryostat system 1 has three cooling stages: a first cooling stage 3, a second cooling stage 4, and a third cooling stage 16. The third cooling stage 16 is at a third cooling temperature that is significantly lower than the temperature of the second cooling stage 4. Thus, the third cooling stage 16 is the coldest cooling stage in the cryostat system 1 of this design. In the illustrated embodiment, the third cooling temperature of the third cooling stage 16 is 1.5 K or less. The SNSPD 2 is designed as described in detail with reference to FIG. 3. In the embodiment of FIG. 5, the SNSPD 2 is located in the third cooling stage 16, i.e., the lowest temperature provided by the cryostat system 1. Nevertheless, in this embodiment, the photovoltaic power converter D1 and the light-emitting diode D2 are located in the first cooling stage 3, which is at a temperature level higher than the third cooling temperature.

[0107] 8 shows one embodiment in which the electronic circuit 19 in the third cooling stage 16 is configured to include a Peltier element 23 in addition to a superconducting quantum interference device 26. The Peltier element 23 is disposed on the third cooling stage 16 at the boundary between the third cooling stage 16 and the first cooling stage 3, with the low-temperature side 24 of the Peltier element 23 located on the third cooling stage 16 and the high-temperature side 25 located on the first cooling stage 3. The Peltier element 23 assists in cooling the third cooling stage 16.

[0108] 6 is a schematic diagram of a design that relies on an array of light emitting devices 18 and an array of photovoltaic converters 17. As previously mentioned, the array of photovoltaic converters 17 supplies power to an electronic circuit 19. The electronic circuit 19 may be located in the same cooling stage as the array of photovoltaic converters 17, or may be located in a further cooling stage at a lower cooling temperature than the first cooling temperature of the first cooling stage. Similarly, the array of light emitting diodes 18 may be located in the same first cooling stage as the array of photovoltaic converters 17, or may be located in a cooling stage at a higher cooling temperature than the first cooling temperature, for example, a second cooling stage at a second cooling temperature.

[0109] The optical power fiber 13 is demultiplexed at chip level, i.e. at the first cooling stage, by a demultiplexer 20. This demultiplexing distributes the power electromagnetic wave to all photovoltaic converters in the array 17.

[0110] Conversely, the radiated electromagnetic radiation emitted by each light-emitting element of the array 18 is combined at the chip level into a single radiated electromagnetic radiation optical fiber 14 using a combiner, such as a multiplexer 21. The electronic circuitry 19 is electrically connected to the array of photovoltaic converters 17 and the array of light-emitting diodes 18 by superconducting wiring 22. Similarly, the two arrays 17, 18 are electrically connected by superconducting wiring 22.

[0111] For the purposes of this disclosure, it is pointed out that all features that would be apparent to a person skilled in the art from the present description, drawings and claims, even if specifically described only in connection with certain further features, can be combined individually and in any desired combination with other features or feature groups disclosed herein, unless expressly excluded or such a combination is impossible or meaningless due to technical circumstances. A comprehensive and explicit description of all possible feature combinations is omitted here for the sake of brevity and readability of the description.

[0112] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are by way of example only and are not intended to limit the scope of protection defined by the claims. The invention is not limited to the disclosed embodiments.

[0113] Variations of the disclosed embodiments will be apparent to those skilled in the art from the drawings, the description and the appended claims. In the claims, the word "comprises" does not exclude other elements or steps, and the indefinite article "one" or "a" does not exclude a plurality. The mere fact that certain features are claimed in different claims does not exclude their combination. Reference signs appearing in the claims do not limit the scope of protection. [Explanation of symbols]

[0114] 1. Cryostat system 2. Superconducting nanowire single-photon detector 3 First cooling stage 4 Second cooling stage 5 Switch 6 DC current source 7 Load Impedance 8. Cryostat 9 cable pairs 10 Surrounding environment 11 Laser 13 Optical fibers for electromagnetic wave transmission 14 Optical fibers for electromagnetic wave emission 15 Photodiode 16 Third cooling stage 17 Array of multiple photoelectric converters 18 Array of multiple light-emitting elements 19 Electronic circuit 20 Demultiplexer 21 Multiplexer 22 Superconducting wiring 23 Peltier element 24 Low temperature side 25 High temperature side 26 Superconducting quantum interference device L k Kinetic Inductance R n Hot Spot Resistance R L heat dissipation resistor D1 Photovoltaic Converter D2 light-emitting diode

Claims

1. A method for supplying electrical energy to an electronic circuit (2), comprising: the electronic circuit (2) is disposed in a first cooling stage (3) of a cryostat system (1) operating at a first cooling temperature, the first cooling temperature being lower than 273 K; The method comprises: generating and emitting power supply electromagnetic radiation at a predetermined location (10) external to said first cooling stage (3); irradiating a photovoltaic converter (D1) with said power supply electromagnetic radiation, said photovoltaic converter (D1) being placed on said first cooling stage (3) and said electronic circuit (2) being electrically connected to said photovoltaic converter (D1); generating a current in said photovoltaic converter (D1); electrically powering or biasing the electronic circuit (2); Including, The method comprises: - transmitting the excess energy introduced into the first cooling stage by the powering electromagnetic radiation to the outside of the first cooling stage (3) by at least one of radiating electromagnetic radiation, electric current or heat transfer driven by said electric current; The method further comprises:

2. The step of transmitting the excess energy includes: generating said radiated electromagnetic radiation in a light-emitting element (D2) driven by said current generated in said photovoltaic converter (D1); emitting said diffused electromagnetic radiation to a predetermined location (10) outside said first cooling stage (3); 2. The method of claim 1, comprising:

3. The step of transmitting the excess energy includes: Electrical resistor (R Ｌ directing said current through a The electrical resistor (R Ｌ 3. The method according to claim 1, wherein the cooling stage (3) is arranged outside the first cooling stage (3).

4. The step of transmitting the excess energy includes:

4. The method according to any one of claims 1 to 3, characterized in that it comprises emitting the radiated electromagnetic radiation from the photovoltaic converter (D1) to a predetermined location (10) outside the first cooling stage (3).

5. The radiating step comprises: Absorbing the power supply electromagnetic radiation in the photovoltaic converter (D1) and re-emitting the dissipated electromagnetic radiation from the photovoltaic converter (D1), or reflecting at least a portion of the powering electromagnetic radiation at the photovoltaic converter (D1) and emitting the reflected powering electromagnetic radiation as the radiated electromagnetic radiation; 5. The method of claim 4, comprising at least:

6. detecting the radiated electromagnetic radiation or the current at a predetermined location external to the first cooling stage; generating a detector signal from the detected radiated electromagnetic radiation or the detected current; determining the state of the electronic circuit (2) from the detector signal; The method according to any one of claims 1 to 5, further comprising:

7. A cryostat system (1), comprising: a first cooling stage (3) operating at a first cooling temperature below 273 K; an electronic circuit (2); a photovoltaic converter (D1) placed on the first cooling stage (3); a radiation source (11) arranged outside the first cooling stage (3); Equipped with the radiation source (11) is installed and arranged such that, during use of the cryostat system (1), power supply electromagnetic radiation is emitted from the radiation source (11) and irradiates the photovoltaic power converter (D1); the electronic circuit (2) is electrically connected to the photovoltaic converter (D1), and the photovoltaic converter (D1) is configured to power or bias the electronic circuit (2) during operation of the cryostat system (1); The cryostat system (1) includes transmitting elements (D2, D1, R Ｌ ) The transmitting elements (D2, D1, R Ｌ ) is electrically connected to or is the photovoltaic converter (D1), The transmitting elements (D2, D1, R Ｌ ) is arranged to transmit excess energy introduced into the first cooling stage by the power supply electromagnetic radiation during operation of the cryostat system (1) to the outside of the first cooling stage by at least radiative electromagnetic radiation, electric current or heat transfer driven by the electric current.

8. the transmitting elements (D2, D1) are arranged to transmit the excess energy as radiated electromagnetic radiation during operation of the cryostat system (1); 8. The cryostat system (1) according to claim 7, characterized in that the cryostat system (1) comprises means for directing the diverging electromagnetic radiation outside the first cooling stage (3).

9. 9. The cryostat system (1) according to claim 8, characterized in that the transmitting element is a light-emitting element (D2) that converts the electric current into the radiated electromagnetic radiation during operation of the cryostat system (1), preferably a light-emitting diode or a laser diode.

10. The cryostat system (1) includes a detector (15) disposed outside the first cooling stage and a controller; the controller is operatively connected to the detector (15) to receive a detector signal from the detector (15) during operation of the cryostat system (1); the detector signal represents a characteristic of the radiated electromagnetic radiation detected by the detector (15); The detector (15) is installed and arranged to detect the radiated electromagnetic radiation emitted from the light-emitting element (D2) during operation of the cryostat system (1); 10. The cryostat system (1) of claim 9, wherein the controller is configured to determine a state of at least the electronic circuit (2) from the detector signal.

11. The transmitting element (R Ｌ 11. The cryostat system (1) according to any one of claims 7 to 10, characterized in that a cooling stage (3) is configured to convert electrical energy into heat during operation of the cryostat system (1) and is arranged outside the first cooling stage (3).

12. the transmitting element is a solid-state heat pump (23); 11. The cryostat system (1) according to any one of claims 7 to 10, characterized in that the solid-state heat pump (23) has a low temperature side (24) located in the first cooling stage (3) and a high temperature side (25) located outside the first cooling stage (3) at a temperature higher than the first cooling temperature.

13. the photovoltaic converter (D1) is the transmitting element (D1), 13. The cryostat system (1) according to any one of claims 7 to 12, characterized in that the photovoltaic converter (D1) is configured to radiate the radiated electromagnetic radiation to a predetermined location outside the first cooling stage (3) during operation of the cryostat system (1).

14. the cryostat system (1) comprises a second cooling stage at a second cooling temperature; the second cooling temperature is lower than 273K and higher than the first cooling temperature; 14. A cryostat system (1) according to any one of claims 7 to 13, characterized in that the photovoltaic converter (D1) is arranged in the first cooling stage and optionally the transmitting element is arranged in the second cooling stage (4).

15. the cryostat system (1) comprises a third cooling stage (16) at a third cooling temperature; the third cooling temperature is lower than the first cooling temperature; The electronic circuit (2) is placed on the third cooling stage (16) and optionally on the transmitting element (D2, R Ｌ 15. The cryostat system (1) according to any one of claims 7 to 14, characterized in that a cooling element (3) is arranged on the first cooling stage (3).

16. A cryostat system (1) according to any one of claims 7 to 15, characterized in that the electronic circuit is a superconducting sensor (2), preferably a superconducting nanowire single photon detector, or the electronic circuit is a superconducting actuator.

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