Optically multiplexed quantum control interface

Abstract

A qubit control system for a quantum computer comprises: an optical waveguide configured to receive and transmit therethrough a wavelength-division multiplexed optical signal having a plurality of modulated optical carriers, each optical carrier at a different optical wavelength and carrying a digital qubit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the multiplexed optical signal to recover the plurality of modulated optical carriers; a plurality of photodetectors in communication with the optical demultiplexer; and a plurality of cryogenic filters in communication with the plurality of photodetectors, each configured to filter a corresponding one of the plurality of digital qubit control signals to provide a corresponding one of the plurality of analog qubit control signals directed to a corresponding superconducting qubit and the photodetector. The cryogenic filters are provided at cryogenic temperatures.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the presently claimed invention relate to quantum computing, and more particularly to methods for controlling qubits in a quantum computer and qubit control systems for quantum computers.

[0002] One building block in quantum computing is the ability to prepare qubits in a particular quantum state. Qubits in superconducting quantum computers are typically controlled using radio frequency energy. Radio frequency energy is delivered via radio frequency lines to a resonator, which in turn interacts with the qubit to control the quantum state of the qubit.

[0003] The number of control radio frequency lines can scale with the number of quantum bits in a quantum computer. For a very large number of quantum bits, the number of radio frequency lines can also be very large. To reduce the number of lines used, it may be desirable to utilize multiplexers and demultiplexers to enable multiple radio frequency energy signals to be sent to multiple quantum bits. However, even when using multiplexers and demultiplexers to transmit radio frequency energy signals, the problem remains that these types of systems are bulky and, more importantly, only allow a limited number of quantum bit signals to be multiplexed (on the order of eight) because quantum bit frequencies are reused throughout the quantum device by non-nearby neighboring quantum bits. Thus, there is a need to solve this and other problems of existing signal transmission techniques. Summary of the Invention

[0004] One aspect of the invention provides a method of controlling quantum bits in a quantum computer, the method comprising the steps of receiving a wavelength division multiplexed optical signal over an optical link, the wavelength division multiplexed optical signal having a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers having a different optical wavelength and each carrying a digital quantum bit control signal; demultiplexing the wavelength division multiplexed optical signal to recover a plurality of modulated optical carriers, each modulated optical carrier carrying a digital quantum bit control signal; detecting the digital quantum bit control signal of each of the plurality of modulated optical carriers with a respective photodetector; filtering the digital quantum bit control signal in each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide an analog quantum bit control signal; and directing the analog quantum bit control signal to a corresponding superconducting quantum bit of a plurality of superconducting quantum bits. The detecting and filtering steps are performed at cryogenic temperatures.

[0005] In one embodiment, filtering the digital qubit control signal on each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide an analog qubit control signal comprises filtering the digital qubit control signal on each of the plurality of modulated optical carriers with a superconducting LC bandpass cryogenic filter to provide an analog qubit control signal.

[0006] In one embodiment, the method further comprises, after filtering the digital qubit control signal in each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide an analog qubit control signal and prior to directing the analog qubit control signal to the corresponding superconducting qubit, attenuating the analog qubit control signal with an attenuator to reduce extraneous microwave energy present in the analog qubit control signal.

[0007] In one embodiment, the detecting and filtering steps are performed at a first cryogenic temperature that is higher than a second cryogenic operating temperature of the corresponding superconducting qubit.

[0008] In one embodiment, the method further comprises electrically multiplexing each analog qubit control signal with an electrical multiplexer to output a single electrical control analog signal to reduce the number of transmission lines required to convey each analog qubit control signal to a corresponding superconducting qubit.

[0009] In one embodiment, receiving the wavelength division multiplexed optical signal through the optical link comprises transmitting the wavelength division multiplexed optical signal through an optical waveguide. In one embodiment, at least one of the detecting and filtering is performed essentially at an operating temperature of the plurality of superconducting qubits. In one embodiment, each of the plurality of superconducting qubits has a control signal in the radio frequency (RF) spectral region.

[0010] Another aspect of the invention provides a qubit control system for a quantum computer. The qubit control system comprises an optical waveguide configured to receive and transmit a wavelength division multiplexed optical signal therethrough, where the wavelength division multiplexed optical signal has a plurality of modulated optical carriers, each optical carrier of the plurality of optical carriers being at a different optical wavelength and carrying a digital qubit control signal; and an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover a plurality of modulated optical carriers, each of which carries a corresponding one of the plurality of digital qubit control signals. The qubit control system further comprises a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect a corresponding one of the plurality of digital qubit control signals; and a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter a corresponding one of the plurality of digital qubit control signals to provide a corresponding one of the plurality of analog qubit control signals. A corresponding one of the plurality of analog qubit control signals is directed to a corresponding one of the plurality of superconducting qubits.A plurality of photodetectors and a plurality of cryogenic filters are provided at the cryogenic temperature.

[0011] In one embodiment, each of the plurality of cryogenic filters comprises a superconducting LC bandpass cryogenic filter.

[0012] In one embodiment, the quantum bit control system further comprises a plurality of attenuators coupled to the plurality of cryogenic filters, each of the plurality of attenuators configured to reduce extraneous microwave energy present in a corresponding one of the plurality of analog quantum bit control signals.

[0013] In one embodiment, the plurality of photodetectors and the plurality of cryogenic filters are provided at a first temperature that is greater than a second cryogenic operating temperature of the plurality of superconducting qubits.

[0014] In one embodiment, each corresponding one of the plurality of analog qubit control signals is in a radio frequency (RF) wavelength range that corresponds to the excitation energy of the corresponding superconducting qubit to be controlled.

[0015] In one embodiment, the quantum bit control system further comprises an electrical multiplexer coupled to the plurality of cryogenic filters, the electrical multiplexer configured to electrically multiplex each analog quantum bit control signal to output a single electrical control analog signal to reduce the number of transmission lines required to convey each analog quantum bit control signal to a corresponding superconducting quantum bit.

[0016] In one embodiment, each photodetector of the plurality of photodetectors is a germanium (Ge) on silicon (Si) photodetector configured to operate in a photovoltaic mode of operation to minimize power dissipation.

[0017] Yet another aspect of the invention provides a quantum computer comprising a cooling system having a temperature controlled enclosure; a quantum processor disposed within the temperature controlled enclosure, the quantum processor having a plurality of quantum bits; and a quantum bit control system extending into the temperature controlled enclosure for providing control of the plurality of quantum bits. The quantum bit control system comprises an optical waveguide configured to receive and transmit wavelength division multiplexed optical signals therethrough, where the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; and an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each optical carrier carrying a corresponding digital quantum bit control signal. The qubit control system further comprises a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect a corresponding digital qubit control signal; and a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter a corresponding digital qubit control signal to provide a corresponding analog qubit control signal. The corresponding analog qubit control signal is directed to a corresponding superconducting qubit of the plurality of superconducting qubits. The plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures within a temperature controlled enclosure.

[0018] In one embodiment, each of the plurality of cryogenic filters comprises a superconducting LC bandpass cryogenic filter.

[0019] In one embodiment, the quantum bit control system further comprises a plurality of attenuators coupled to the plurality of cryogenic filters, each of the plurality of attenuators configured to attenuate extraneous microwave energy present in a corresponding analog quantum bit control signal.

[0020] In one embodiment, the plurality of photodetectors and the plurality of cryogenic filters are provided at a first temperature that is greater than a second cryogenic operating temperature of the plurality of superconducting qubits.

[0021] In one embodiment, the quantum bit control system further comprises an electrical multiplexer coupled to the plurality of cryogenic filters, the electrical multiplexer configured to electrically multiplex each analog quantum bit control signal to output a single electrical control analog signal to reduce the number of transmission lines required to convey each analog quantum bit control signal to a corresponding superconducting quantum bit. [Brief description of the drawings]

[0022] The present disclosure, as well as the method of operation and function of the associated elements of construction, and combination of parts, and economy of manufacture, will become more apparent from a consideration of the following description and the appended claims, with reference to the accompanying drawings, all of which form a part of this specification, and in which like reference characters designate corresponding parts in the various drawings, It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.

[0023] [Figure 1] FIG. 1 is a schematic diagram of a qubit control system for a quantum computer in accordance with an embodiment of the present invention.

[0024] [Figure 2A] FIG. 2 is a schematic diagram showing types of connections for a cryogenic filter according to an embodiment of the present invention. [Figure 2B] FIG. 2 is a schematic diagram showing types of connections for a cryogenic filter according to an embodiment of the present invention.

[0025] [Diagram 3] FIG. 1 is a schematic diagram illustrating connection of a cryogenic filter to an attenuator prior to connection to a qubit chip having multiple qubits, in accordance with an embodiment of the present invention.

[0026] [Figure 4] FIG. 1 is a schematic diagram of a quantum computer according to an embodiment of the present invention.

[0027] [Diagram 5] 4 is a flowchart of a method for controlling qubits in a quantum computer according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] In the following paragraphs, the terms "light" and "optical" are intended to be general to include both the visible and non-visible portions of the electromagnetic spectrum, such as, but not limited to, visible light, infrared light, near infrared light, and ultraviolet light.

[0029] FIG. 1 is a schematic diagram of a qubit control system 100 for a quantum computer (not shown) according to an embodiment of the present invention. The qubit control system 100 comprises an optical waveguide 102 configured to receive and transmit a wavelength division multiplexed optical signal 104 therethrough. The wavelength division multiplexed signal 104 comprises a plurality of modulated optical carriers 104A. Each optical carrier of the plurality of modulated optical carriers 104A is at a different optical wavelength (λ1, λ2, ...) and carries a digital qubit control signal. The example in FIG. 1 has eight optical carriers demultiplexed by the ring resonator 104A into eight different wavelengths (λ1, λ2, ..., λ8). However, the broad concepts of the present invention are not limited to any particular number of optical carriers or optical demultiplexing scheme. There may be more or less than eight, without limitation.

[0030] In one embodiment, the light source (not shown in FIG. 1 ) may include, for example, multiple lasers. The multiple lasers may include, but are not limited to, Fabry-Perot gain medium lasers that may be used to generate appropriately spaced optical wavelengths (λ1, λ2, ...) in the optical waveguide 102. For example, a quantum dot-based diode laser operating as an optical frequency comb generator may be used. The quantum dot-based laser may be coupled to an optical waveguide (e.g., an optical fiber) to provide, for example, several low noise 80 GHz spaced optical modes, for example, at about 1310 nm. However, any number of lasers (one, two, or more) may also be used, and each laser may be configured to deliver one or multiple optical wavelengths. Regardless of how the multiple optical wavelengths are generated, they are each modulated at room temperature with a specific quantum bit control signal.

[0031] Qubit control system 100 also includes an optical demultiplexer (DEMUX) 106 optically coupled to optical waveguide 102 for receiving wavelength division multiplexed optical signal 104 after transmission through optical waveguide 102 to recover a plurality of modulated optical carriers 104A, each carrying a corresponding one of a plurality of digital qubit control signals. Optical DEMUX 106 may, for example, in some embodiments have a ring resonator structure coupled to optical waveguide 102 through evanescent radiation. However, the general concepts of the present invention are not limited to only this embodiment.

[0032] The quantum bit control system 100 further comprises a plurality of photodetectors (PD) 108 in communication with the optical demultiplexer (DEMUX) 106. Each of the plurality of photodetectors (PD) 108 is configured to detect a corresponding one of the plurality of digital quantum bit control signals. The quantum bit control system 100 also comprises a plurality of cryogenic filters 110 in communication with the plurality of photodetectors (PD) 108. Each of the plurality of cryogenic filters 110 is configured to filter a corresponding one of the plurality of digital quantum bit control signals to provide a corresponding one of a plurality of analog quantum bit control signals (at frequencies v1, v2, ...). The corresponding one of the plurality of analog quantum bit control signals is directed to a corresponding superconducting quantum bit (not shown in FIG. 1) of the plurality of superconducting quantum bits. The plurality of photodetectors (PD) 108 and the plurality of cryogenic filters 110 are provided at cryogenic temperatures.

[0033] In one embodiment, a number of photodetectors (PD) 108 are in communication with the optical demultiplexer (DEMUX) 106 via a number of optical fibers 107, each optical fiber carrying a corresponding modulated optical carrier 104A at a particular optical wavelength (λ1, λ2, ...). In one embodiment, each photodetector (PD) 108 may be a germanium (Ge)-on-silicon (Si) photodetector configured to operate in a photovoltaic mode of operation to minimize power dissipation. In one embodiment, the photodetectors (PD) 108 may also be photodiodes, photomultipliers, or bolometer scales.

[0034] In one embodiment, the plurality of cryogenic filters 110 are coupled to a plurality of photodetectors (PDs) 108 via a plurality of electrical waveguides 109 (e.g., microwave or radio frequency waveguides). The plurality of electromagnetic waveguides 109 are configured to convey digital qubit control signals to the plurality of cryogenic filters 110.

[0035] 2A and 2B are schematic diagrams illustrating types of connections for a cryogenic filter 110 according to an embodiment of the present invention. In one embodiment, each of the cryogenic filters 110 comprises a superconducting LC bandpass cryogenic filter. In one embodiment, the LC bandpass cryogenic filter is connected to the photodetector 108 to receive a digital qubit control signal (e.g., including a plurality of voltage radio frequency pulses) and output an analog qubit control signal (e.g., a modulated sine wave).

[0036] 3 is a schematic diagram illustrating the connection of a cryogenic filter 110 to an attenuator 112 prior to connection to a qubit chip 114 having multiple qubits, according to one embodiment of the present invention. In one embodiment, the qubit control system 100 comprises multiple attenuators 112 coupled to multiple cryogenic filters (e.g., LC cryogenic filters) 110 and to the qubit chip 114. Each of the multiple attenuators 112 is configured to reduce extraneous microwave (e.g., radio frequency) energy present in a corresponding analog qubit control signal output by the cryogenic filter 110 prior to inputting the analog qubit control signal to the qubit chip 114.

[0037] In one embodiment, the photodetectors 108 and the cryogenic filters 110 are provided at a first temperature that is higher than a second cryogenic operating temperature of the superconducting qubits. For example, as shown in FIG. 3, the cryogenic filters 110 are provided at a first temperature that is about 700 mK and the superconducting qubits (qubit chips) 114 are provided at a lower second temperature of about 15 mK. In one embodiment, the attenuator 112 may be provided at an intermediate cryogenic temperature between the temperature of the cryogenic filters 110 and the temperature of the qubit chips 114. For example, as shown in FIG. 3, the attenuator 112 may be provided at a temperature of about 100 mK. In another embodiment, the attenuator 112 may be provided at the first temperature of the cryogenic filters 110 (e.g., 700 mK) or at the second temperature of the superconducting qubits (e.g., 15 mK) or at any temperature between the first and second temperatures. Furthermore, if the photodetector 108 and the cryogenic filter 110 are at a first temperature (e.g., 700 mK) stage that is different from a second temperature (e.g., 15 mK) stage of the plurality of superconducting qubits, then the attenuator 112 may be provided at either or both of the cryogenic filter temperature stage and the plurality of superconducting qubit temperature stage.

[0038] In one embodiment, the corresponding analog qubit control signal is in a radio frequency (RF) wavelength range that corresponds to the excitation energy of the corresponding qubit to be controlled among the plurality of qubits in qubit chip 114.

[0039] 1, qubit control system 100 may also include an electrical multiplexer 120 coupled to the multiple cryogenic filters 110. Electrical multiplexer 120 is configured to electrically multiplex each analog qubit control signal output by cryogenic filters 110 to output a single electrical control analog signal to reduce the number of transmission lines required to convey each analog qubit control signal to a corresponding superconducting qubit.

[0040] Another aspect of the invention is to provide a quantum computer 200. FIG. 4 is a schematic diagram of quantum computer 200, according to one embodiment of the invention. Quantum computer 200 includes a cooling system 202 including a temperature-controlled enclosure 204 and a quantum processor 206 disposed within temperature-controlled enclosure 204. Quantum processor 206 includes a plurality of qubits 208. Quantum computer 200 further includes a qubit control system 210 that extends into temperature-controlled enclosure 204 to provide control of the plurality of qubits 208. Quantum bit control system 210 is similar in many aspects to qubit control system 100 described in the paragraph above. Thus, it should be appreciated that many of the features described above with respect to qubit control system 100 can also be utilized with respect to qubit control system 210.

[0041] Qubit control system 210 comprises optical waveguide 212 configured to receive and transmit wavelength division multiplexed optical signal 214 therethrough. Wavelength division multiplexed signal 214 comprises a plurality of modulated optical carriers 214A. Each optical carrier of the plurality of optical carriers 214A is at a different optical wavelength (λ1, λ2, ...) and carries a digital qubit control signal.

[0042] In one embodiment, a light source 212A including multiple lasers, such as, for example, Fabry-Perot gain medium lasers, may be used to generate appropriately spaced optical wavelengths (λ 1 , λ 2 , . . . ) in the optical waveguide 212 .

[0043] Quantum bit control system 100 also includes an optical demultiplexer (DEMUX) 216 optically coupled to optical waveguide 212 for receiving wavelength division multiplexed optical signal 214 after transmission through optical waveguide 212 to recover a plurality of modulated optical carriers 214A, each carrying a corresponding one of a plurality of digital quantum bit control signals.

[0044] The qubit control system 210 further includes a plurality of photodetectors (PD) 218 ​​in communication with the optical demultiplexer 216. Each of the plurality of photodetectors (PD) 218 ​​is configured to detect a corresponding one of the plurality of digital qubit control signals. The qubit control system 210 also includes a plurality of cryogenic filters 220 in communication with the plurality of photodetectors (PD) 218. Each of the plurality of cryogenic filters 220 is configured to filter a corresponding one of the plurality of corresponding digital qubit control signals to provide a corresponding one of the plurality of analog qubit control signals. The corresponding one of the plurality of analog qubit control signals is directed to a corresponding superconducting qubit 208 of the plurality of superconducting qubits in the quantum processor 206. The plurality of photodetectors (PD) 218 ​​and the plurality of cryogenic filters 220 are provided at cryogenic temperatures.

[0045] In one embodiment, the photodetectors (PD) 218 ​​are in communication with the optical demultiplexer 216 via a plurality of optical waveguides 217, each optical waveguide carrying a corresponding modulated optical carrier 104A at a particular optical wavelength (λ1, λ2, ...). In one embodiment, each photodetector (PD) 218 ​​may be a germanium (Ge)-on-silicon (Si) photodetector configured to operate in a photovoltaic mode of operation to minimize power dissipation. In one embodiment, each photodetector 108 may also be a photodiode, photomultiplier, or bolometer scale.

[0046] In one embodiment, the plurality of cryogenic filters 220 are coupled to the plurality of photodetectors (PDs) 218 ​​via a plurality of electromagnetic waveguides (e.g., microwave or radio frequency waveguides) 219. The plurality of electromagnetic waveguides 219 are configured to convey digital qubit control signals to the plurality of cryogenic filters 220.

[0047] The corresponding analog qubit control signals (at frequencies v1, v2, ...) output by each of the plurality of cryogenic filters 220 are directed to corresponding superconducting qubits in the plurality of superconducting qubits 208 within the quantum processor 206. The plurality of photodetectors (PDs) 218 ​​and the plurality of cryogenic filters 220 are provided at cryogenic temperatures within the temperature controlled enclosure 204.

[0048] In one embodiment, photodetectors 218 and cryogenic filters 220 are provided in temperature-controlled enclosure 204 at a first temperature higher than the second cryogenic operating temperature 208 of the superconducting qubits. For example, temperature-controlled enclosure 204 may be provided with multiple compartments, and qubits 208 may be located in one compartment at one temperature, while photodetectors 218 and cryogenic filters 220 may be located in another compartment at a different temperature. For example, cryogenic filters 220 may be provided at a first temperature that is about 700 mK, and superconducting qubits 208 may be provided at a second temperature of about 15 mK.

[0049] In one embodiment, the qubit control system 210 may also include a plurality of attenuators 222 coupled to the plurality of cryogenic filters (e.g., LC cryogenic filters) 220 and to the plurality of qubits 208 in the quantum processor 206. Each of the plurality of attenuators 222 is configured to reduce extraneous microwave (e.g., radio frequency) energy present in a corresponding analog qubit control signal output by the cryogenic filter 220 prior to input to the quantum processor 206. In one embodiment, the attenuator 222 may be provided at an intermediate cryogenic temperature in another compartment or region within the temperature-controlled vessel 204 between the temperature of the cryogenic filter 220 and the temperature of the plurality of qubits 208 in the quantum processor 206. For example, the attenuator 222 may be provided at a temperature of about 100 mK. In another embodiment, the attenuator 222 may be provided at a first temperature (e.g., 700 mK) of the cryogenic filter 220 or at a second temperature (e.g., 15 mK) of the plurality of superconducting qubits 208 or at any temperature between the first and second temperatures. Furthermore, if photodetector 218 and cryogenic filter 220 are at a first temperature (e.g., 700 mK) stage that is different from a second temperature (e.g., 15 mK) stage of the plurality of superconducting qubits 208, attenuator 222 may be provided at either or both of the cryogenic filter temperature stage and the plurality of superconducting qubit temperature stage.

[0050] In another embodiment, attenuator 222 may be provided at the first temperature (e.g., 700 mK) of cryogenic filter 220 or at the second temperature (e.g., 15 mK) of plurality of superconducting qubits 208 or at any temperature between the first and second temperatures. Furthermore, if photodetector 218 and cryogenic filter 220 are at a first temperature (e.g., 700 mK) stage that is different from the second temperature (e.g., 15 mK) stage of plurality of superconducting qubits 208, attenuator 222 may be provided at either or both the cryogenic filter temperature stage and the plurality of superconducting qubit temperature stage.

[0051] 5 is a flow chart of a method of controlling qubits in a quantum computer according to an embodiment of the invention. The method comprises, at S300, receiving a wavelength division multiplexed optical signal over an optical link, where the wavelength division multiplexed optical signal has a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers having a different optical wavelength and each carrying a digital qubit control signal. The method further comprises, at S302, demultiplexing the wavelength division multiplexed optical signal to recover a plurality of modulated optical carriers, each of which carries a digital qubit control signal. The method also comprises, at S304, detecting a respective digital qubit control signal of the plurality of optical carriers with a respective photodetector, and, at S306, filtering the digital qubit control signal in each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide an analog qubit control signal. The method further comprises, at S308, directing the analog qubit control signal to a corresponding superconducting qubit of a plurality of superconducting qubits. The detecting and filtering steps are performed at cryogenic temperatures.

[0052] In one embodiment, filtering the digital qubit control signal on each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide an analog qubit control signal comprises filtering the digital qubit control signal on each of the plurality of modulated optical carriers with a superconducting LC bandpass cryogenic filter to provide an analog qubit control signal.

[0053] The method further comprises, after filtering the digital qubit control signal on each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide an analog qubit control signal and prior to directing the analog qubit control signal to the corresponding superconducting qubit, attenuating the analog qubit control signal with an attenuator to reduce extraneous microwave energy present in the analog qubit control signal. In one embodiment, the detecting and filtering steps are performed at a first cryogenic temperature that is higher than a second cryogenic operating temperature of the corresponding superconducting qubit.

[0054] In one embodiment, the method further comprises electrically multiplexing each analog qubit control signal with an electrical multiplexer to output a single electrical control analog signal to reduce the number of transmission lines required to convey each analog qubit control signal to a corresponding superconducting qubit.

[0055] In one embodiment, receiving the wavelength division multiplexed optical signal through the optical link comprises transmitting the wavelength division multiplexed optical signal through an optical waveguide. In one embodiment, at least one of the detecting and filtering is performed essentially at an operating temperature of the plurality of superconducting qubits. In one embodiment, each of the plurality of superconducting qubits has a control signal in the radio frequency (RF) spectral region.

[0056] Although the description of various embodiments of the present invention has been presented for illustrative purposes, they are not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terms used in this specification are selected to best explain the principles of the embodiments, the practical application of the technology found in the market, or technical improvements thereto, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method of receiving, by an optical demultiplexer coupled to an optical link, a wavelength division multiplexed optical signal through the optical link, wherein the wavelength division multiplexed optical signal has a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers having a different optical wavelength and each carrying a digital quantum bit control signal; demultiplexing the wavelength division multiplexed optical signal with a ring resonator for each optical carrier in the optical demultiplexer to recover the multiple modulated optical carriers, each of which carries the digital quantum bit control signal; detecting the digital quantum bit control signal for each of the plurality of modulated optical carriers with a respective photodetector; filtering the digital qubit control signals on each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide analog qubit control signals; and directing the analog qubit control signal to a corresponding superconducting qubit among a plurality of superconducting qubits. Equipped with The steps of detecting and filtering are performed at cryogenic temperatures. A method for controlling quantum bits in a quantum computer.

2. A method for controlling quantum bits in a quantum computer, comprising: receiving a wavelength division multiplexed optical signal over an optical link, the wavelength division multiplexed optical signal having a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers having a different optical wavelength and each carrying a digital quantum bit control signal; demultiplexing the wavelength division multiplexed optical signal to recover the plurality of modulated optical carriers, each carrying a digital quantum bit control signal; detecting the digital quantum bit control signal for each of the plurality of modulated optical carriers with a respective photodetector; filtering the digital qubit control signals on each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide analog qubit control signals; and directing the analog qubit control signal to a corresponding superconducting qubit among a plurality of superconducting qubits. Equipped with the detecting and filtering steps are performed at cryogenic temperatures; filtering the digital qubit control signal on each of the plurality of modulated optical carriers with the corresponding cryogenic filter to provide the analog qubit control signal comprises filtering the digital qubit control signal on each of the plurality of modulated optical carriers with a superconducting LC bandpass cryogenic filter to provide the analog qubit control signal. A method for controlling quantum bits in a quantum computer.

3. receiving a wavelength division multiplexed optical signal over an optical link, the wavelength division multiplexed optical signal having a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers having a different optical wavelength and each carrying a digital quantum bit control signal; demultiplexing the wavelength division multiplexed optical signal to recover the plurality of modulated optical carriers, each carrying a digital quantum bit control signal; detecting the digital quantum bit control signal for each of the plurality of modulated optical carriers with a respective photodetector; filtering the digital qubit control signals on each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide analog qubit control signals; attenuating the analog qubit control signal using an attenuator to reduce extraneous microwave energy present in the analog qubit control signal; and directing the analog qubit control signal to a corresponding superconducting qubit among a plurality of superconducting qubits. Equipped with The steps of detecting and filtering are performed at cryogenic temperatures. A method for controlling quantum bits in a quantum computer.

4. receiving a wavelength division multiplexed optical signal over an optical link, the wavelength division multiplexed optical signal having a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers having a different optical wavelength and each carrying a digital quantum bit control signal; demultiplexing the wavelength division multiplexed optical signal to recover the plurality of modulated optical carriers, each carrying a digital quantum bit control signal; detecting the digital quantum bit control signal for each of the plurality of modulated optical carriers with a respective photodetector; filtering the digital qubit control signals on each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide analog qubit control signals; and directing the analog qubit control signal to a corresponding superconducting qubit among a plurality of superconducting qubits. Equipped with the detecting and filtering steps are performed at cryogenic temperatures; the detecting and filtering steps are performed at a first cryogenic temperature that is greater than a second cryogenic operating temperature of the corresponding superconducting qubit. A method for controlling quantum bits in a quantum computer.

5. A method for controlling a quantum bit in a quantum computer, comprising: receiving a wavelength division multiplexed optical signal over an optical link, the wavelength division multiplexed optical signal having a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers having a different optical wavelength and each carrying a digital quantum bit control signal; demultiplexing the wavelength division multiplexed optical signal to recover the plurality of modulated optical carriers, each carrying a digital quantum bit control signal; detecting the digital quantum bit control signal for each of the plurality of modulated optical carriers with a respective photodetector; filtering the digital qubit control signals on each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide analog qubit control signals; and directing the analog qubit control signal to a corresponding superconducting qubit among a plurality of superconducting qubits. Equipped with the detecting and filtering steps are performed at cryogenic temperatures; The method further comprises electrically multiplexing each analog qubit control signal with an electrical multiplexer to output a single electrical control analog signal to reduce the number of transmission lines required to convey each analog qubit control signal to the corresponding superconducting qubit.

6. receiving a wavelength division multiplexed optical signal over an optical link, the wavelength division multiplexed optical signal having a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers having a different optical wavelength and each carrying a digital quantum bit control signal; demultiplexing the wavelength division multiplexed optical signal to recover the plurality of modulated optical carriers, each carrying a digital quantum bit control signal; detecting the digital quantum bit control signal for each of the plurality of modulated optical carriers with a respective photodetector; filtering the digital qubit control signals on each of the plurality of modulated optical carriers with a corresponding cryogenic filter to provide analog qubit control signals; and directing the analog qubit control signal to a corresponding superconducting qubit among a plurality of superconducting qubits. Equipped with the detecting and filtering steps are performed at cryogenic temperatures; At least one of the detecting and filtering steps is performed essentially at an operating temperature of the plurality of superconducting qubits. A method for controlling quantum bits in a quantum computer.

7. 7. A method according to claim 1, wherein receiving the wavelength division multiplexed optical signal over the optical link comprises transmitting the wavelength division multiplexed optical signal over an optical waveguide.

8. 8. The method of claim 1, wherein each of the plurality of superconducting qubits has a control signal in the radio frequency (RF) spectral range.

9. An optical waveguide configured to receive and transmit wavelength division multiplexed optical signals, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide to receive the wavelength division multiplexed optical signal after transmission through the optical waveguide, the optical demultiplexer using its respective ring resonators to recover the plurality of modulated optical carriers, each of the modulated optical carriers carrying a corresponding one of a plurality of digital quantum bit control signals; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect a corresponding one of the plurality of digital qubit control signals; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding one of the plurality of digital qubit control signals to provide a corresponding one of a plurality of analog qubit control signals; Equipped with The corresponding one of the plurality of analog qubit control signals is directed to a corresponding one of a plurality of superconducting qubits, and the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures. A qubit control system for quantum computers.

10. An optical waveguide configured to receive and transmit wavelength division multiplexed optical signals, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each of which carries a corresponding one of a plurality of digital quantum bit control signals; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect a corresponding one of the plurality of digital qubit control signals; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding one of the plurality of digital qubit control signals to provide a corresponding one of a plurality of analog qubit control signals; Equipped with the corresponding one of the plurality of analog qubit control signals is directed to a corresponding one of a plurality of superconducting qubits, the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures; each of the plurality of cryogenic filters comprises a superconducting LC bandpass cryogenic filter; A qubit control system for quantum computers.

11. An optical waveguide configured to receive and transmit wavelength division multiplexed optical signals, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each of which carries a corresponding one of a plurality of digital quantum bit control signals; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect a corresponding one of the plurality of digital qubit control signals; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding one of the plurality of digital qubit control signals to provide a corresponding one of a plurality of analog qubit control signals; Equipped with the corresponding one of the plurality of analog qubit control signals is directed to a corresponding one of a plurality of superconducting qubits, the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures; and a plurality of attenuators coupled to the plurality of cryogenic filters, each of the plurality of attenuators configured to reduce extraneous microwave energy present in the corresponding one of the plurality of analog qubit control signals. A qubit control system for quantum computers.

12. An optical waveguide configured to receive and transmit wavelength division multiplexed optical signals, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each of which carries a corresponding one of a plurality of digital quantum bit control signals; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect a corresponding one of the plurality of digital qubit control signals; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding one of the plurality of digital qubit control signals to provide a corresponding one of a plurality of analog qubit control signals; Equipped with the corresponding one of the plurality of analog qubit control signals is directed to a corresponding one of a plurality of superconducting qubits, the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures; the plurality of photodetectors and the plurality of cryogenic filters are provided at a first temperature greater than a second cryogenic operating temperature of the plurality of superconducting qubits. A qubit control system for quantum computers.

13. An optical waveguide configured to receive and transmit wavelength division multiplexed optical signals, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each of which carries a corresponding one of a plurality of digital quantum bit control signals; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect a corresponding one of the plurality of digital qubit control signals; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding one of the plurality of digital qubit control signals to provide a corresponding one of a plurality of analog qubit control signals; Equipped with the corresponding one of the plurality of analog qubit control signals is directed to a corresponding one of a plurality of superconducting qubits, the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures; and an electrical multiplexer coupled to the plurality of cryogenic filters, the electrical multiplexer configured to electrically multiplex each analog qubit control signal to output a single electrical control analog signal to reduce a number of transmission lines required to convey each analog qubit control signal to the corresponding superconducting qubit. A qubit control system for quantum computers.

14. An optical waveguide configured to receive and transmit wavelength division multiplexed optical signals, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each of the modulated optical carriers carrying a corresponding one of a plurality of digital quantum bit control signals; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect a corresponding one of the plurality of digital qubit control signals; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding one of the plurality of digital qubit control signals to provide a corresponding one of a plurality of analog qubit control signals; Equipped with the corresponding one of the plurality of analog qubit control signals is directed to a corresponding one of a plurality of superconducting qubits, the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures; each photodetector of the plurality of photodetectors is a germanium (Ge)-on-silicon (Si) photodetector configured to operate in a photovoltaic mode of operation to minimize power dissipation; A qubit control system for quantum computers.

15. 15. The quantum bit control system of claim 9, wherein each of the corresponding ones of the plurality of analog quantum bit control signals is in a radio frequency (RF) wavelength range corresponding to an excitation energy of the corresponding superconducting quantum bit to be controlled.

16. a cooling system having a temperature controlled reservoir; a quantum processor disposed within the temperature controlled enclosure, the quantum processor having a plurality of qubits; and a qubit control system extending into the temperature controlled enclosure to provide control of the plurality of qubits; Equipped with The quantum bit control system includes: an optical waveguide configured to receive and transmit wavelength division multiplexed optical signals therethrough, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide to receive the wavelength division multiplexed optical signal after transmission through the optical waveguide, the optical demultiplexer using its respective ring resonators to recover the plurality of modulated optical carriers, each of the modulated optical carriers carrying a corresponding one of a plurality of digital quantum bit control signals; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect the corresponding digital qubit control signal; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding digital qubit control signal to provide a corresponding analog qubit control signal; having The corresponding analog qubit control signal is directed to a corresponding superconducting qubit of a plurality of superconducting qubits, and the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures within the temperature controlled enclosure. Quantum computer.

17. a cooling system having a temperature controlled reservoir; a quantum processor disposed within the temperature controlled enclosure, the quantum processor having a plurality of qubits; and a qubit control system extending into the temperature controlled enclosure to provide control of the plurality of qubits; Equipped with The quantum bit control system includes: an optical waveguide configured to receive and transmit wavelength division multiplexed optical signals therethrough, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each of which carries a corresponding digital quantum bit control signal; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect the corresponding digital qubit control signal; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding digital qubit control signal to provide a corresponding analog qubit control signal; having the corresponding analog qubit control signal is directed to a corresponding superconducting qubit of a plurality of superconducting qubits, the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures within the temperature controlled enclosure; each of the plurality of cryogenic filters comprises a superconducting LC bandpass cryogenic filter; Quantum computer.

18. a cooling system having a temperature controlled reservoir; a quantum processor disposed within the temperature controlled enclosure, the quantum processor having a plurality of qubits; and a qubit control system extending into the temperature controlled enclosure to provide control of the plurality of qubits; Equipped with The quantum bit control system includes: an optical waveguide configured to receive and transmit wavelength division multiplexed optical signals therethrough, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each of which carries a corresponding digital quantum bit control signal; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect the corresponding digital qubit control signal; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding digital qubit control signal to provide a corresponding analog qubit control signal; having the corresponding analog qubit control signal is directed to a corresponding superconducting qubit of a plurality of superconducting qubits, the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures within the temperature controlled enclosure; and a plurality of attenuators coupled to the plurality of cryogenic filters, each of the plurality of attenuators configured to attenuate extraneous microwave energy present in the corresponding analog qubit control signal. Quantum computer.

19. a cooling system having a temperature controlled reservoir; a quantum processor disposed within the temperature controlled enclosure, the quantum processor having a plurality of qubits; and a qubit control system extending into the temperature controlled enclosure to provide control of the plurality of qubits; Equipped with The quantum bit control system includes: an optical waveguide configured to receive and transmit wavelength division multiplexed optical signals therethrough, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each of which carries a corresponding digital quantum bit control signal; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect the corresponding digital qubit control signal; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding digital qubit control signal to provide a corresponding analog qubit control signal; having the corresponding analog qubit control signal is directed to a corresponding superconducting qubit of a plurality of superconducting qubits, the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures within the temperature-controlled enclosure; the plurality of photodetectors and the plurality of cryogenic filters are provided at a first temperature greater than a second cryogenic operating temperature of the plurality of superconducting qubits. Quantum computer.

20. a cooling system having a temperature controlled reservoir; a quantum processor disposed within the temperature controlled enclosure, the quantum processor having a plurality of qubits; and a qubit control system extending into the temperature controlled enclosure to provide control of the plurality of qubits; Equipped with The quantum bit control system includes: an optical waveguide configured to receive and transmit wavelength division multiplexed optical signals therethrough, wherein the wavelength division multiplexed optical signals have a plurality of modulated optical carriers, each optical carrier of the plurality of modulated optical carriers being at a different optical wavelength and carrying a digital quantum bit control signal; an optical demultiplexer optically coupled to the optical waveguide for receiving the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical carriers, each of which carries a corresponding digital quantum bit control signal; a plurality of photodetectors in communication with the optical demultiplexer, each of the plurality of photodetectors configured to detect the corresponding digital qubit control signal; a plurality of cryogenic filters in communication with the plurality of photodetectors, each of the plurality of cryogenic filters configured to filter the corresponding digital qubit control signal to provide a corresponding analog qubit control signal; having the corresponding analog qubit control signal is directed to a corresponding superconducting qubit of a plurality of superconducting qubits, the plurality of photodetectors and the plurality of cryogenic filters are provided at cryogenic temperatures within the temperature controlled enclosure; and an electrical multiplexer coupled to the plurality of cryogenic filters, the electrical multiplexer configured to electrically multiplex each analog qubit control signal to output a single electrical control analog signal to reduce a number of transmission lines required to convey each analog qubit control signal to the corresponding superconducting qubit. Quantum computer.

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