Optical multiplexed quantum control
By controlling qubits with optical signals and utilizing optical multiplexers and radio frequency filters, the problems of numerous radio frequency lines and noise and heat have been solved, enabling more efficient qubit control in quantum computers.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INTERNATIONAL BUSINESS MACHINE CORPORATION
- Filing Date
- 2021-09-10
- Publication Date
- 2026-07-31
AI Technical Summary
In existing quantum computers, the large number of radio frequency circuits and the introduction of heat and noise into the quantum superconducting environment result in a large and undesirable system.
Optical multiplexers and demultiplexers are used to control qubits through optical signals. Wavelength division multiplexing and demultiplexing are achieved using optical waveguides and optical modulators. Combined with radio frequency multiplexers and filters, multiple qubits are separated and controlled.
The number of radio frequency lines was reduced, the impact of heat and noise on qubits was reduced, and the efficiency and controllability of the system were improved.
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Figure CN116171536B_ABST
Abstract
Description
Technical Field
[0001] The presently claimed embodiments of the invention relate to quantum computing, and more specifically to a qubit control system for a quantum computer and a method for controlling qubits in a quantum computer. Background Technology
[0002] A building block in quantum computing is the ability to create qubits in specific quantum states. In superconducting quantum computers, qubits are typically controlled using radio frequency (RF) energy. This RF energy is delivered via RF circuitry to a resonator, which in turn interacts with the qubit to control its quantum state.
[0003] The number of control radio frequency (RF) lines can be proportional to the number of qubits in a quantum computer. With a very large number of qubits, the number of RF lines can also become extremely large. To reduce the number of lines used, it might be desirable to employ multiplexers and demultiplexers to enable the transmission of multiple RF energy signals to those multiple qubits. However, even when using multiplexers and demultiplexers to transmit RF energy signals, the following problems remain: these types of systems are bulky, and more importantly, they introduce heat and associated noise into the superconducting environment of these qubits. Therefore, it is desirable to address this and other issues of existing signal transmission technologies. Summary of the Invention
[0004] An aspect of the present invention is to provide a qubit control system for a quantum computer. The qubit control system includes a source of multiple optical carriers, each optical carrier being light of a different wavelength; and an optical modulator configured to receive the multiple optical carriers and modulate each optical carrier with a qubit control signal to provide multiple modulated optical signals. The qubit control system also includes an optical multiplexer configured to receive the multiple modulated optical signals and provide wavelength division multiplexed optical signals; and an optical waveguide optically coupled to the optical multiplexer to receive and transmit the wavelength division multiplexed optical signals. The qubit control system further includes an optical demultiplexer optically coupled to the optical waveguide to receive the wavelength division multiplexed optical signal after transmission through the waveguide, to recover each of the plurality of modulated optical signals; a demodulator optically coupled to the optical demultiplexer to receive each of the recovered plurality of modulated optical signals to output corresponding plurality of recovered qubit control signals; and a plurality of spatially separated qubit control waveguides, each configured to receive at least one of the plurality of recovered qubit control signals, such that equivalent recovered qubit control signals are spatially divided into different spatially separated qubit control waveguides. Each of the plurality of spatially separated qubit control waveguides directs a qubit control signal to a different subset of a plurality of qubits, which are configured to be controlled by the qubit control signals transmitted by the plurality of spatially separated qubit control waveguides.
[0005] In this embodiment, the plurality of qubit control signals and the corresponding plurality of recovered qubit control signals are within the radio frequency (RF) wavelength range corresponding to the excitation energy of the corresponding qubit to be controlled.
[0006] In one embodiment, the qubit control system further includes a radio frequency multiplexer configured to receive at least two recovered qubit control signals from the demodulator, the qubit control signals being different RF wavelengths, and to multiplex the at least two recovered qubit control signals onto one of the plurality of spatially separated qubit control waveguides.
[0007] In one embodiment, the qubit control system further includes a plurality of radio frequency multiplexers, each configured to receive at least two recovered qubit control signals from the demodulator, the qubit control signals being different RF wavelengths, and to multiplex the at least two recovered qubit control signals onto a corresponding one of the plurality of spatially separated qubit control waveguides.
[0008] In one embodiment, the radio frequency multiplexer includes multiple bandpass filters, each allowing one corresponding recovered qubit control signal to pass through while attenuating or substantially blocking all other recovered qubit control signals. In another embodiment, the demodulator includes a direct photoelectric converter.
[0009] Another aspect of the present invention is to provide a quantum computer comprising: a cooling system having a temperature-controlled container; a quantum processor disposed within the temperature-controlled container, the quantum processor including a plurality of qubits; and a qubit control system having a portion outside the temperature-controlled container and a portion extending into the temperature-controlled container to provide control over the plurality of qubits.
[0010] The qubit control system includes: a source having multiple optical carriers, each optical carrier being light of a different wavelength; an optical modulator configured to receive the multiple optical carriers and modulate each optical carrier with qubit control signals to provide multiple modulated optical signals; an optical multiplexer configured to receive the multiple modulated optical signals and provide wavelength division multiplexed optical signals; an optical waveguide optically coupled to the optical multiplexer to receive and transmit the wavelength division multiplexed optical signals therethrough; an optical demultiplexer optically coupled to the optical waveguide to receive the wavelength division multiplexed optical signals transmitted through the optical waveguide to recover each of the multiple modulated optical signals; a demodulator optically coupled to the optical demultiplexer to receive each of the recovered multiple modulated optical signals to output corresponding multiple recovered qubit control signals; and a plurality of spatially separated qubit control waveguides, each qubit control waveguide configured to receive at least one of the multiple recovered qubit control signals, such that equivalent recovered qubit control signals are spatially divided into different spatially separated qubit control waveguides. Each of the plurality of spatially separated qubit control waveguides directs a qubit control signal to a different subset of the plurality of qubits, which are configured to be controlled by the qubit control signal transmitted by the plurality of spatially separated qubit control waveguides.
[0011] In one embodiment, the sources of multiple optical carriers, the optical modulator, and the optical multiplexer are all disposed outside the temperature-controlled container. In another embodiment, the optical demultiplexer and demodulator are disposed inside the temperature-controlled container. In yet another embodiment, the optical waveguide extends from the optical multiplexer disposed outside the temperature-controlled container to the optical demultiplexer inside the container. In still another embodiment, the multiple qubit control signals and the corresponding multiple recovered qubit control signals are within a radio frequency (RF) wavelength range corresponding to the excitation energy of the corresponding qubit to be controlled.
[0012] In one embodiment, the quantum computer further includes a radio frequency (RF) multiplexer configured to receive at least two recovered qubit control signals of different RF wavelengths from the demodulator, and to multiplex the at least two recovered qubit control signals onto one of the plurality of spatially separated qubit control waveguides. In another embodiment, the quantum computer further includes a plurality of RF multiplexers, each configured to receive at least two recovered qubit control signals of different RF wavelengths from the demodulator, and to multiplex the at least two recovered qubit control signals onto a corresponding one of the plurality of spatially separated qubit control waveguides.
[0013] In one embodiment, the radio frequency multiplexer includes multiple bandpass filters, each bandpass filter allowing a corresponding recovered qubit control signal to pass through while attenuating or substantially blocking all other recovered qubit control signals. In another embodiment, the demodulator includes a direct photoelectric detector. In yet another embodiment, the cooling system further includes a second temperature-controlled container to be controlled at a temperature higher than that of the first mentioned temperature-controlled container. At least one of the optical multiplexer, the optical modulator, and the optical multiplexer from the sources of the multiple optical carriers is arranged within the second temperature-controlled container.
[0014] In one embodiment, the sources of multiple optical carriers, the optical modulator, and the optical multiplexer are all disposed within a second temperature-controlled container. In another embodiment, the cooling system further includes a second temperature controller to maintain a temperature higher than that in the first-mentioned temperature-controlled container. In another embodiment, an optical demultiplexer and at least one demodulator are disposed within the second temperature-controlled container. In yet another embodiment, the optical demultiplexer and all demodulators are disposed within the second temperature-controlled container.
[0015] Another aspect of the present invention provides a method for controlling qubits in a quantum computer. The method includes: modulating each of a plurality of qubit control signals onto a corresponding optical carrier of a plurality of optical carriers to provide a plurality of modulated optical signals, each of the plurality of optical carriers being light of a different wavelength; multiplexing the plurality of modulated optical signals onto an optical waveguide to provide a wavelength division multiplexed optical signal to be transmitted through the optical waveguide; demultiplexing the plurality of modulated optical signals after transmission through the optical waveguide from the wavelength division multiplexed optical signal to recover the plurality of modulated optical signals; demodulating the recovered plurality of modulated optical signals to recover the plurality of qubit control signals; after demodulation, coupling each recovered qubit control signal from the plurality of recovered qubit control signals to at least one of a plurality of spatially separated qubit control waveguides, such that equivalent qubit control signals are spatially divided into different qubit control waveguides; and directing the recovered qubit control signals from each spatially separated qubit control waveguide to different subsets of the plurality of qubits of the quantum computer to provide control thereon.
[0016] In this embodiment, modulation and multiplexing are performed at a temperature higher than that of demultiplexing, demodulation, coupling, and guiding. In this embodiment, the plurality of qubits are a plurality of superconducting qubits, and at least one of the demultiplexing, demodulation, coupling, and guiding is performed at the operating temperature of the plurality of superconducting qubits. In this embodiment, each of the plurality of superconducting qubits has a control signal in the radio frequency (RF) spectral range, and the qubit control waveguides are RF waveguides.
[0017] In an embodiment, demultiplexing multiple modulated optical signals from a wavelength division multiplexed optical signal includes: bandpass filtering the wavelength division multiplexed optical signal in each of a plurality of passbands to provide multiple demultiplexed modulated optical signals at each of a plurality of optical channels.
[0018] In one embodiment, demodulating multiple quantum bit control signals from multiple modulated optical signals includes: directly optically detecting each of the multiple demultiplexed modulated optical signals to provide corresponding multiple demodulated electrical signals within the RF spectrum.
[0019] In one embodiment, demodulating the plurality of qubit control signals from the plurality of modulated optical signals includes direct optical detection to provide corresponding plurality of demodulated electrical signals within the RF spectral range. In another embodiment, the demodulation, coupling, and guidance are performed at the operating superconducting temperature of the plurality of qubits. Attached Figure Description
[0020] The operation and function of the relevant elements of this disclosure, as well as the economy of combination and manufacture of the components, will become more apparent when the following description and appended claims are considered in conjunction with the accompanying drawings, all of which form part of this specification, wherein similar reference numerals denote corresponding components in the various drawings. However, it should be clearly understood that the drawings are for illustrative and descriptive purposes only and are not intended to be limiting of the invention.
[0021] Figure 1 This is a schematic diagram of a qubit control system for a quantum computer according to an embodiment of the present invention;
[0022] Figure 2 This is a schematic diagram of a quantum computer according to an embodiment of the present invention; and
[0023] Figure 3 This is a flowchart of a method for controlling qubits in a quantum computer according to an embodiment of the present invention. Detailed Implementation
[0024] In the following paragraphs, the terms “light” and “optics” are intended to be general to include both the visible and invisible portions of the electromagnetic spectrum, such as, but not limited to, visible light, infrared light, near-infrared light, and ultraviolet light. The term “subset of a plurality of qubits” is intended to include any integer that includes a single qubit or any plurality of qubits.
[0025] Figure 1 This 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 includes a light source 102 with multiple optical carriers 102A, each optical carrier being light of a different wavelength. In embodiments, the light source 102 may include, for example, multiple lasers, such as Fabry-Perot gain medium lasers. For example, lasers with quantum dot active regions can be used to generate appropriately spaced optical wavelengths in a single optical fiber. These light sources are suitable for generating multiple laser lines (e.g., 8 to 32 laser lines) over a relatively narrow range of optical wavelengths. For example, a quantum dot-based diode laser operating as an optical frequency comb generator can be used. The quantum dot-based laser can be coupled to an optical fiber to provide, for example, several low-noise 80 GHz spaced optical modes at approximately 1310 nm.
[0026] The qubit control system 100 also includes an optical modulator 104 configured to receive the plurality of optical carriers 102A and modulate each optical carrier 102A with a qubit control signal 106A generated by a qubit control signal source 106 to provide a plurality of modulated optical signals 108A.
[0027] The qubit control system 100 also includes an optical multiplexer (MUX) 108 configured to receive the plurality of modulated optical signals 108A and provide wavelength division multiplexed optical signals 108B. The qubit control system 100 also includes an optical waveguide 109 optically coupled to the optical multiplexer for receiving and transmitting wavelength division multiplexed optical signals therethrough.
[0028] The qubit control system 100 further includes an optical demultiplexer (DEMUX) 110, which is optically coupled to the optical waveguide 109 to receive the wavelength division multiplexed optical signal 108B after transmission through the optical waveguide 109, so as to recover each of the plurality of modulated optical signals 108A.
[0029] The qubit control system 100 also includes a demodulator 112 optically coupled to the optical demultiplexer 110 to receive each of the recovered plurality of modulated optical signals 108A to output corresponding plurality of recovered qubit control signals 106B. In an embodiment, the plurality of recovered qubit control signals 106B are substantially similar to or equivalent to the qubit control signals 106A.
[0030] The qubit control system 100 further includes a plurality of spatially separated qubit control waveguides 111, each qubit control waveguide 111 being configured to receive at least one of the plurality of recovered qubit control signals 106B, such that the equivalent recovered qubit control signals 106B are spatially divided into different spatially separated qubit control waveguides 111.
[0031] The qubit control system 100 is configured to control a plurality of qubits 116 via qubit control signals 106A delivered by a plurality of spatially separated qubit control waveguides 111. Each of the plurality of spatially separated qubit control waveguides 111 directs a qubit control signal 106B to a different subset 116A of the plurality of qubits 116. Although a single qubit is shown as a subset of the qubits 116A of the plurality of qubits 116, it must be understood that two or more qubits can form a subset of the qubits 116A of the plurality of qubits 116.
[0032] In one embodiment, the qubit control system 100 further includes a radio frequency multiplexer / demultiplexer 114, which includes one or more bandpass filters 114B configured to receive a plurality of recovered qubit control signals 106B transmitted through spatially separated qubit control waveguides 111 and output frequency-filtered recovered qubit control signals 114A, which are used to control a corresponding subset 116A of the plurality of qubits 116.
[0033] In this embodiment, the plurality of qubit control signals 106A and the corresponding plurality of recovered qubit control signals 106B are within the radio frequency (RF) wavelength range corresponding to the excitation energy of the corresponding qubit 116A to be controlled.
[0034] In an embodiment, the qubit control system 100 further includes a radio frequency multiplexer / demultiplexer 114 configured to receive at least two recovered qubit control signals 106B with different RF wavelengths from a demodulator 112 and multiplex the at least two recovered qubit control signals 106B onto one of the plurality of spatially separated qubit control waveguides 111.
[0035] In an embodiment, the qubit control system 100 further includes a plurality of radio frequency multiplexers / demultiplexers 114, each radio frequency multiplexer / demultiplexer 114 being configured to receive at least two recovered qubit control signals 106B of different RF wavelengths from the demodulator 112, and to multiplex the at least two recovered qubit control signals 106B onto a corresponding one of the plurality of spatially separated qubit control waveguides 111.
[0036] In one embodiment, the radio frequency multiplexer 114 includes a plurality of bandpass filters 114B, each of which allows a corresponding qubit control signal of one of the recovered qubit control signals 106B to pass through, while attenuating or substantially blocking all other recovered qubit control signals 106B. In another embodiment, each bandpass filter 114B may include LC circuitry to provide an LC bandpass filter.
[0037] In one embodiment, demodulator 112 includes a direct photoelectric converter. In another embodiment, the photoelectric converter may include, for example, an optical detector or photodetector such as a photodiode, photomultiplier tube, or radiative thermal measurement scale (SC).
[0038] Another aspect of the present invention is to provide a quantum computer 200. Figure 2This is a schematic diagram of a quantum computer according to an embodiment of the present invention. The quantum computer 200 includes a cooling system 202, which includes a temperature-controlled container 204 and a quantum processor 206 disposed within the temperature-controlled container 204. The quantum processor 206 includes a plurality of qubits 208. The quantum computer 200 also includes a qubit control system 210, which has a portion 210A outside the temperature-controlled container 204 and a portion 210B extending into the temperature-controlled container 204 to provide control over the plurality of qubits 208.
[0039] The quantum bit control system 210 is similar to the one mentioned above. Figure 1 The qubit control system 100 is described. Therefore, when referring to components of the qubit control system 210, reference is made instead to similar components of the qubit control system 100. Therefore, further reference is made to... Figure 1 The qubit control system 210 includes a light source 102 with multiple optical carriers 102A, each optical carrier 102A being light of a different wavelength. The qubit control system 210 also includes an optical modulator 104 configured to receive the multiple optical carriers 102A and modulate each optical carrier 102A with a qubit control signal 106A to provide the multiple modulated optical signals 108A.
[0040] The qubit control system 210 also includes an optical multiplexer 108 configured to receive the plurality of modulated optical signals 108A and provide the wavelength division multiplexed optical signal 108B. The qubit control system 210 further includes an optical waveguide 109 optically coupled to the optical multiplexer for receiving and transmitting the wavelength division multiplexed optical signal therethrough.
[0041] The qubit control system 210 further includes an optical demultiplexer 110 optically coupled to the optical waveguide 109 to receive the wavelength division multiplexed optical signal 108B after transmission through the optical waveguide 109 to recover each of the plurality of modulated optical signals 108A.
[0042] The qubit control system 210 also includes a demodulator 112 optically coupled to the optical demultiplexer 110 to receive each of the recovered plurality of modulated optical signals 108A to output corresponding plurality of recovered qubit control signals 106B.
[0043] The qubit control system 100 further includes the plurality of spatially separated qubit control waveguides 111, each qubit control waveguide being configured to receive at least one of the plurality of recovered qubit control signals 106B, such that the equivalent recovered qubit control signals 106B are spatially divided into different spatially separated qubit control waveguides 111.
[0044] The plurality of qubits 208 are configured to be controlled by qubit control signals transmitted by the plurality of spatially separated qubit control waveguides 111. Each of the plurality of spatially separated qubit control waveguides 111 directs the qubit control signal to a different subset 208A of the plurality of qubits 208. In an embodiment, each of the plurality of spatially separated qubit control waveguides 111 directs the qubit control signal to a different subset of the plurality of qubits 208.
[0045] In this embodiment, the light source 102 of the plurality of optical carriers 102A, the optical modulator 104, and the optical multiplexer 108 are all disposed outside the temperature-controlled container 204. In this embodiment, the optical demultiplexer 110 and the demodulator 112 are disposed inside the temperature-controlled container 204. The optical waveguide 109 extends from the optical multiplexer 108 disposed outside the temperature-controlled container 204 into the temperature-controlled container 204, reaching the optical demultiplexer 110.
[0046] In this embodiment, the plurality of qubit control signals 106A and the corresponding plurality of recovered qubit control signals 106B are within the radio frequency (RF) wavelength range corresponding to the excitation energy of the corresponding qubit 208A to be controlled.
[0047] In one embodiment, the quantum computer 200 further includes a radio frequency (RF) multiplexer 212 configured to receive at least two recovered qubit control signals 106B with different RF wavelengths from the demodulator 112 and multiplex the at least two recovered qubit control signals 106B onto one of the plurality of spatially separated qubit control waveguides 111. The RF multiplexer 212 may be similar to Figure 1 The radio frequency multiplexer 114 shown and described in the preceding paragraphs.
[0048] The quantum computer 200 further includes a plurality of radio frequency multiplexers 212, each configured to receive at least two recovered qubit control signals 106B of different RF wavelengths from the demodulator 112, and to multiplex the at least two recovered qubit control signals 106B onto a corresponding one of the plurality of spatially separated qubit control waveguides 111.
[0049] In one embodiment, the radio frequency multiplexer 212 includes a plurality of bandpass filters, such as bandpass filter 114B of radio frequency multiplexer 114, each of which allows a corresponding one of the recovered qubit control signals 106B to pass through while attenuating or substantially blocking all other recovered qubit control signals 106B. In another embodiment, the bandpass filter may include LC circuitry to form an LC bandpass filter.
[0050] In one embodiment, the cooling system 202 further includes a second temperature-controlled container 205, which is controlled at a temperature higher than that in the first-mentioned temperature-controlled container 204. In another embodiment, the internal portion 210B of the qubit control system 210 includes an optical multiplexer 108, an optical modulator 104, and an optical demultiplexer 110 and is housed within the second temperature-controlled container 205.
[0051] In another embodiment, the light source 102, optical modulator 104, and optical multiplexer 108 of the plurality of optical carriers 102A may also be disposed in the second temperature-controlled container 205. In this embodiment, the second temperature-controlled container 205 is controlled at a higher temperature than that in the first-mentioned temperature-controlled container 204 where the quantum processor 206 is located. In one embodiment, the optical demultiplexer 110 and at least one demodulator 112 may also be disposed in the second temperature-controlled container 205 instead of the first-mentioned temperature-controlled container 204. In this embodiment, both the optical demultiplexer 110 and the demodulator 112 are disposed in the second temperature-controlled container 205.
[0052] Although the second temperature-controlled container 205 is shown inside the first-mentioned temperature-controlled container 204, the second temperature-controlled container 205 may also be located outside the first-mentioned temperature-controlled container 204. Furthermore, in another embodiment, the second temperature-controlled container 205 may also be a part or region of the first-mentioned temperature-controlled container 204, wherein the temperature is higher than the portion or region of the first-mentioned temperature-controlled container 204 where the quantum processor 206 is located or positioned. In this embodiment, the quantum processor 206 and its associated qubits 208 and 116 operate at superconducting temperatures, and therefore these qubits 116 and 208 are superconducting qubits.
[0053] In other embodiments, more than one temperature-controlled container can be used, without being limited to a specific number. Furthermore, in different embodiments, multiple components of the qubit control system can be arranged in various ways within more than one temperature-controlled container.
[0054] The advantage of using such qubit control systems 100 and 210 is that they provide more signal / fiber capacity than could be achieved using multiplexed signal radio frequency (RF) coaxial cables, because wavelength division multiplexing (WDM) allows the transmission of the same modulation frequency RF at different optical wavelengths. Another benefit is that high-frequency finite impulse response (FIR) and infinite impulse response (I1R) modulation can be performed in the optical domain at room temperature or in an environment with temperatures higher than the temperature of the quantum processor / qubit. Yet another benefit is that the relatively small signal path for these signals before filtering at low temperatures allows for the elimination of active electronics in the cryostat, thus reducing heat dissipation. Instead, passive LC filters and photodetectors / converters can be used within the cryostat.
[0055] Another aspect of the present invention is to provide a method for controlling qubits in a quantum computer. Figure 3 This is a flowchart of a method for controlling qubits in a quantum computer according to an embodiment of the present invention. The method includes: at 300, modulating each of a plurality of qubit control signals onto a corresponding optical carrier of a plurality of optical carriers to provide a plurality of modulated optical signals, each of the plurality of optical carriers being light of a different wavelength; at 302, multiplexing the plurality of modulated optical signals onto an optical waveguide to provide a wavelength division multiplexed optical signal to be transmitted through the optical waveguide; at 304, demultiplexing the plurality of modulated optical signals from the wavelength division multiplexed optical signal after transmission through the optical waveguide to recover the plurality of modulated optical signals; and at 306, demultiplexing the recovered plurality of... The modulated optical signal is demodulated to recover the plurality of qubit control signals; at 308, after demodulation, each recovered qubit control signal from the plurality of recovered qubit control signals is coupled to at least one of a plurality of spatially separated qubit control waveguides, such that the equivalent qubit control signals are spatially divided into different qubit control waveguides; and at 310, the recovered qubit control signals from each spatially separated qubit control waveguide are directed to different subsets of the plurality of qubits of the quantum computer to provide control over them.
[0056] In this embodiment, modulation and multiplexing are performed at a temperature higher than that for demultiplexing, demodulation, coupling, and guiding. In this embodiment, the plurality of qubits are a plurality of superconducting qubits, and at least one of the demultiplexing, demodulation, coupling, and guiding is performed at the operating temperature of the plurality of superconducting qubits. In this embodiment, each of the plurality of superconducting qubits has a control signal in the radio frequency (RF) spectral range, and the qubit control waveguides are RF waveguides.
[0057] In an embodiment, demultiplexing multiple modulated optical signals from a wavelength division multiplexed optical signal includes: bandpass filtering the wavelength division multiplexed optical signal for each of a plurality of passbands to provide a plurality of demultiplexed modulated optical signals at each of a plurality of optical channels.
[0058] In one embodiment, demodulating multiple quantum bit control signals from multiple modulated optical signals includes: directly optically detecting each of the multiple demultiplexed modulated optical signals to provide corresponding multiple demodulated electrical signals within the RF spectrum.
[0059] In one embodiment, demodulating the plurality of qubit control signals from the plurality of modulated optical signals includes direct optical detection to provide corresponding plurality of demodulated electrical signals within the RF spectral range.
[0060] Various embodiments of the invention have been described for illustrative purposes, but 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 terminology used herein has been chosen to best explain the principles of the embodiments, their practical application, or technical improvements to the technology found in the market, or to enable those skilled in the art to understand the embodiments disclosed herein.
Claims
1. A qubit control system for a quantum computer, comprising: A source with multiple optical carriers, each of which is light of a different wavelength; An optical modulator configured to receive the plurality of optical carriers and modulate each optical carrier with a qubit control signal in order to provide a plurality of modulated optical signals; An optical multiplexer configured to receive the plurality of modulated optical signals and provide wavelength division multiplexed optical signals; An optical waveguide, optically coupled to the optical multiplexer, for receiving and transmitting the wavelength division multiplexed optical signal therethrough; An optical demultiplexer, optically coupled to the optical waveguide, to receive the wavelength division multiplexed optical signal transmitted through the optical waveguide, in order to recover each of the plurality of modulated optical signals; A demodulator, optically coupled to the optical demultiplexer, is used to receive each of the recovered multiple modulated optical signals to output corresponding multiple recovered qubit control signals. Multiple spatially separated qubit control waveguides, each configured to receive at least one of multiple recovered qubit control signals, such that the equivalent recovered qubit control signals are spatially divided into different spatially separated qubit control waveguides. Each of the plurality of spatially separated qubit control waveguides directs a qubit control signal to a different subset of the plurality of qubits, the plurality of qubits being configured to be controlled by the qubit control signal transmitted by the plurality of spatially separated qubit control waveguides.
2. The qubit control system according to claim 1, wherein the plurality of qubit control signals and the corresponding plurality of recovered qubit control signals are within the radio frequency (RF) wavelength range corresponding to the excitation energy of the corresponding qubit to be controlled.
3. The qubit control system of claim 2, further comprising a radio frequency multiplexer configured to receive at least two recovered qubit control signals from the demodulator, the at least two recovered qubit control signals being different RF wavelengths, and to multiplex the at least two recovered qubit control signals onto one of the plurality of spatially separated qubit control waveguides.
4. The qubit control system according to claim 2, further comprising a plurality of radio frequency multiplexers, each of the plurality of radio frequency multiplexers being configured to receive at least two recovered qubit control signals from the demodulator, the at least two recovered qubit control signals being different RF wavelengths, and to multiplex the at least two recovered qubit control signals onto one of the plurality of spatially separated qubit control waveguides.
5. The quantum bit control system according to claim 3 or 4, wherein, The radio frequency multiplexer includes multiple bandpass filters, each of which allows a corresponding recovered qubit control signal to pass through while attenuating or blocking all other recovered qubit control signals.
6. The quantum bit control system according to any one of claims 1-4, wherein, The demodulator includes a direct photoelectric converter.
7. A quantum computer, comprising: Refrigeration system, the refrigeration system including a temperature-controlled container; A quantum processor, comprising a plurality of qubits, is disposed within the temperature-controlled container. as well as A qubit control system having a portion outside the temperature-controlled container and a portion extending into the temperature-controlled container to provide control over the plurality of qubits. The qubit control system mentioned above includes: A source with multiple optical carriers, each of which is light of a different wavelength; An optical modulator configured to receive the plurality of optical carriers and modulate each optical carrier with a qubit control signal to provide a plurality of modulated optical signals; An optical multiplexer configured to receive the plurality of modulated optical signals and provide wavelength division multiplexed optical signals; An optical waveguide, optically coupled to the optical multiplexer, for receiving and transmitting the wavelength division multiplexed optical signal therethrough; An optical demultiplexer, optically coupled to the optical waveguide, to receive the wavelength division multiplexed optical signal transmitted through the optical waveguide, in order to recover each of the plurality of modulated optical signals; A demodulator, optically coupled to the optical demultiplexer, is provided to receive each of the recovered multiple modulated optical signals to output corresponding multiple recovered qubit control signals. Multiple spatially separated qubit control waveguides, each configured to receive at least one of multiple recovered qubit control signals, such that the equivalent recovered qubit control signals are spatially divided into different spatially separated qubit control waveguides. Each of the plurality of spatially separated qubit control waveguides directs a qubit control signal to a different subset of the plurality of qubits, the plurality of qubits being configured to be controlled by the qubit control signal transmitted by the plurality of spatially separated qubit control waveguides.
8. The quantum computer according to claim 7, wherein, The sources, optical modulators, and optical multiplexers of the plurality of optical carriers are all disposed outside the temperature-controlled container. The optical demultiplexer and the demodulator are disposed inside the temperature-controlled container, and The optical waveguide extends from the optical multiplexer arranged outside the temperature-controlled container to the optical demultiplexer inside the temperature-controlled container.
9. The quantum computer according to claim 8, wherein, The plurality of qubit control signals and the corresponding plurality of recovered qubit control signals are in the radio frequency (RF) wavelength range corresponding to the excitation energy of the corresponding qubit to be controlled.
10. The quantum computer of claim 9, further comprising a radio frequency multiplexer configured to receive at least two recovered qubit control signals having different RF wavelengths from the demodulator, and to multiplex the at least two recovered qubit control signals onto one of the plurality of spatially separated qubit control waveguides.
11. The quantum computer of claim 9, further comprising a plurality of radio frequency multiplexers, each of the plurality of radio frequency multiplexers being configured to receive from the demodulator at least two recovered qubit control signals of different RF wavelengths, and to multiplex the at least two recovered qubit control signals onto a corresponding one of the plurality of spatially separated qubit control waveguides.
12. The quantum computer according to claim 11, wherein, The radio frequency multiplexer includes multiple bandpass filters, each of which allows a corresponding recovered qubit control signal to pass through while attenuating or blocking all other recovered qubit control signals.
13. The quantum computer according to any one of claims 8 to 12, wherein, The demodulator includes a direct photodetector.
14. The quantum computer according to any one of claims 8 to 12, wherein, The refrigeration system further includes an additional temperature-controlled container, which is controlled at a temperature higher than that in the temperature-controlled container. In this embodiment, at least one of the optical multiplexer, the optical modulator, and the optical multiplexer from the sources of the plurality of optical carriers is arranged in the additional temperature-controlled container.
15. The quantum computer according to claim 14, wherein, The sources, optical modulators, and optical multiplexers of the plurality of optical carriers are all arranged in the additional temperature-controlled container.
16. The quantum computer according to any one of claims 8 to 12, wherein, The refrigeration system further includes an additional temperature-controlled container, which is controlled at a temperature higher than that in the temperature-controlled container. The optical demultiplexer and at least one demodulator are arranged in the additional temperature-controlled container.
17. The quantum computer according to claim 16, wherein, The optical demultiplexer and all of the demodulators are arranged in the additional temperature-controlled container.
18. A method for controlling qubits in a quantum computer, comprising: Each of the multiple quantum bit control signals is modulated onto a corresponding optical carrier of the multiple optical carriers to provide multiple modulated optical signals, wherein each of the multiple optical carriers is light of a different wavelength. The multiple modulated optical signals are multiplexed onto the optical waveguide to provide wavelength division multiplexed optical signals to be transmitted through the optical waveguide; The multiple modulated optical signals in the wavelength division multiplexed optical signal after transmission through the optical waveguide are demultiplexed to recover the signals of the multiple modulated optical signals; The recovered multiple modulated optical signals are demodulated to recover the multiple quantum bit control signals; After demodulation, each recovered qubit control signal from the recovered plurality of qubit control signals is coupled to at least one of a plurality of spatially separated qubit control waveguides, such that the equivalent qubit control signals are spatially divided into different qubit control waveguides; and The recovered qubit control signals from each spatially separated qubit control waveguide are directed to different subsets of multiple qubits of the quantum computer to provide its control.
19. The method according to claim 18, wherein, The modulation and multiplexing are performed at a higher temperature than the demultiplexing, demodulation, coupling, and booting.
20. The method of claim 18 or 19, wherein the plurality of qubits are a plurality of superconducting qubits, and at least one of the demultiplexing, the demodulation, the coupling, and the guiding is performed at the operating temperature of the plurality of superconducting qubits.
21. The method of claim 19, wherein each of the plurality of qubits has a control signal in the radio frequency (RF) spectrum range, and the qubit control waveguide is an RF waveguide.
22. The method according to claim 20, wherein, The demultiplexing of the plurality of modulated optical signals from the wavelength division multiplexed optical signal includes: filtering the wavelength division multiplexed optical signal for each of the plurality of passbands to provide a plurality of demultiplexed modulated optical signals at each of the plurality of optical channels.
23. The method according to claim 22, wherein, The demodulation from the plurality of quantum bit control signals of the plurality of modulated optical signals includes: direct optical detection of each of the plurality of demultiplexed modulated optical signals to provide a plurality of corresponding demodulated electrical signals in the RF spectral range.
24. The method according to claim 22, wherein, The demodulation of the plurality of quantum bit control signals from the plurality of modulated optical signals includes direct optical detection to provide a plurality of corresponding demodulated electrical signals within the RF spectral range.
25. The method according to claim 21, wherein, The demodulation, coupling, and guidance are performed at the operating superconducting temperature of the plurality of qubits.