Integrated control and readout circuit for superconducting QUBITS

Abstract

Integrated drive and readout circuit arrangement (100), the arrangement comprising: directional couplers (104_1, 104_2, 104_N) configured to connect to qubit resonator systems (102_1, 102_2, 102_N), each directional coupler comprising a first terminal (103A), a second terminal (103B), a third terminal (103C) and a fourth terminal (103D), the first terminal being configured to receive a qubit signal and a readout signal, the second terminal being configured to connect to a corresponding qubit resonator system, the third terminal being configured to connect to a corresponding diplexer, and the fourth terminal being an isolated terminal;Diplexers (106_1, 106_2, 106_N) connected to the directional couplers, each diplexer comprising a low-pass band terminal (105B) connected to a termination, a high-pass band terminal (105C), and a common terminal (105A) connected to the corresponding directional couplers, the common terminal being configured to support both low- and high-frequency bands belonging to the low-pass band terminal and the high-pass band terminal, respectively, the diplexers being configured to direct a reflected drive microwave signal to the low-pass band terminal; and a microwave signal combiner (108) connected to the high-pass band terminal of each diplexer, the microwave signal combiner being configured to combine microwave signals from the diplexers.

Description

BACKGROUND

[0001] The present invention relates generally to superconducting electronic units and in particular to integrated control and readout circuits for superconducting qubits.

[0002] The fundamental element of a quantum computer is the quantum bit, also known as a "qubit." Unlike a classical bit, which represents zero and one, a qubit can also represent a quantum superposition of these two states. Within the laws of quantum physics, these states can be formalized as the probability of being in either state. Accordingly, these states can be manipulated and observed within the framework of quantum physics.

[0003] In cavity quantum electrodynamics, quantum data processing uses nonlinear, superconducting units called qubits to process and store quantum information at microwave frequencies. Resonators (e.g., a two-dimensional (2D) planar waveguide or a three-dimensional (3D) microwave cavity) are used to read out qubits and enable interaction between them. For example, each superconducting qubit can contain one or more Josephson junctions, where capacitors are connected in parallel across the junctions. The qubits are capacitively coupled to the resonators (e.g., 2D or 3D microwave cavities).

[0004] The electromagnetic energy associated with the qubit is stored in the Josephson junctions and in the capacitive and inductive elements that comprise the qubit. In one example, to read the qubit state, a microwave signal is applied to the microwave readout cavity, coupling to the qubit at the cavity frequency corresponding to the qubit state. The transmitted (or reflected) microwave signal passes through several thermal isolation stages and low-noise amplifiers, which are necessary to eliminate or reduce noise and improve the signal-to-noise ratio. The microwave signal is measured at room temperature. The amplitude and / or phase of the returned / output microwave signal can carry information about the qubit state, depending on the readout scheme. This readout signal can be measured and analyzed using electronics at room temperature.Microwave readout provides a stable signal amplitude for control, and off-the-shelf (COTS) hardware is available.

[0005] Quantum systems such as superconducting qubits are highly sensitive to electromagnetic interference, particularly in the microwave and infrared ranges. To protect these quantum systems from microwave and infrared interference, several layers are used for filtering, attenuation, and insulation. Of particular interest are the protective layers used on the input and output lines (I / O lines), also known as transmission lines, which are connected to the quantum system and carry the input and output signals to and from it. In superconducting qubits, these I / O lines (transmission lines) are typically microwave coaxial cables or waveguides.Some of the techniques or components used to eliminate or attenuate the noise that propagates or penetrates these transmission lines include attenuators, circulators, insulators, low-pass microwave filters, band-pass microwave filters, and infrared filters based on lossy absorption materials or dispersive elements. An integrated drive and readout circuit is required to drive and read out the superconducting qubits with a minimal number of input and output transmission lines and a minimal number of components. SUMMARY

[0006] One embodiment of the present invention relates to an integrated control and readout circuit arrangement. A non-limiting example of the integrated control and readout circuit arrangement includes directional couplers configured to connect to qubit resonator systems, diplexers connected to the directional couplers, and a microwave signal combiner connected to the diplexers.

[0007] Another embodiment of the present invention relates to a method for forming an integrated control and readout circuit arrangement. A non-limiting example of the method includes providing directional couplers configured to connect to qubit resonator systems, connecting diplexers to the directional couplers, and connecting a microwave signal combiner to the diplexers.

[0008] Another embodiment of the present invention is directed to a chip. A non-limiting example of the chip includes directional couplers configured to connect to qubit resonator systems, diplexers connected to the directional couplers, and a microwave signal combiner connected to the diplexers.

[0009] Another embodiment of the present invention relates to a method for driving qubit resonator systems. A non-limiting example of the method involves transmitting microwave signals to the qubit resonator systems via directional couplers, receiving the microwave signals again by the directional couplers (the microwave signals having been reflected by the qubit resonator systems), and receiving the microwave signals from the directional couplers by diplexers. The diplexers are configured to direct the microwave signals to a termination element.

[0010] Another embodiment of the present invention relates to a method for reading out qubit resonator systems. A non-limiting example of the method includes transmitting microwave signals to the qubit resonator systems via directional couplers, receiving the microwave signals again by the directional couplers (where the microwave signals have been reflected by the qubit resonator systems), receiving the microwave signals from the directional couplers via diplexers, and receiving the microwave signals from the diplexers via a microwave signal combiner. The microwave signal combiner is configured to combine the microwave signals into compound microwave signals. The method also includes transmitting the compound microwave signals via the microwave signal combiner to a quantum-limited amplifier. List of characters Fig. Figure 1 is a schematic representation of an integrated control and readout circuit illustrating the readout of superconducting qubits according to embodiments of the present invention. Fig. Figure 2 is a schematic representation of the integrated control and readout circuit illustrating the control of the superconducting qubits according to the embodiments of the present invention. Fig. Figure 3 is a schematic representation of the integrated control and readout circuit according to embodiments of the present invention. Fig. Figure 4 is a schematic representation of a signal combiner according to embodiments of the present invention. Fig. Figure 5 is a schematic representation of a signal combiner according to embodiments of the present invention. Fig. Figure 6 is a flowchart of a method for forming an integrated control and readout circuit according to embodiments of the present invention. Fig. Figure 7 is a flowchart of a method for controlling qubit resonator systems according to embodiments of the present invention. Fig. Figure 8 is a flowchart of a method for reading out qubit resonator systems according to embodiments of the present invention. DETAILED DESCRIPTION

[0011] Various embodiments are described here with reference to the accompanying drawings. Alternative embodiments may be developed without exceeding the scope of this document. It is noted that various connections and positional relationships (e.g., above, below, next to, etc.) between elements are specified in the following description and in the drawings. These connections and / or positional relationships may be direct or indirect unless otherwise specified and are not intended to be restrictive in this respect. Accordingly, a connection between entities may refer to a direct or an indirect connection, and a positional relationship between entities may be a direct or an indirect positional relationship. As an example of an indirect positional relationship, references to forming the layer “ A “ above the layer “ B“Situations in which one or more intermediate shifts (e.g., a shift “ C “) between a layer “ A “ and a layer “ B “ as long as the relevant properties and functionalities of the layer are maintained” A “ and the layer “ B “ not significantly altered by the intermediate layer(s)).

[0012] Several physical objects have been proposed as possible implementations of qubits. However, solid-state circuits, particularly superconducting circuits, are of great interest because they offer scalability that allows for the fabrication of circuits with a larger number of interacting qubits. Superconducting qubits are typically based on Josephson junctions (JJ). A Josephson junction consists of two superconductors coupled, for example, by a thin insulating barrier. A Josephson junction can be fabricated using an insulating tunnel barrier, such as Al₂O₃, between superconducting electrodes. For such Josephson junctions, the maximum allowable supercurrent is the critical current. I c .

[0013] Embodiments are configured to build a scalable qubit drive and readout circuit where the number of output and control lines of the circuit is minimized. Embodiments provide techniques for building a scalable qubit drive and readout circuit that can be integrated together on the same printed circuit board or chip.

[0014] Additionally, embodiments are configured to minimize the number of circulators and isolators. These embodiments also provide a scalable qubit drive and readout circuit that is readily optimized, replaceable, and thermally optimized. To emphasize the size / space of the circulators and isolators, a typical cryogenic isolator measures approximately 8.5 cm x 3.1 cm x 1.7 cm and weighs about 229.5 grams. A copper clamp, weighing approximately 183.1 g, is used to thermalize the cryogenic isolator. A typical cryogenic circulator measures approximately 4.5 cm x 3.5 cm x 1.8 cm and weighs about 41.2 g. In a typical setup with 1 input and 1 output line connecting 1 qubit resonator and 1 quantum-limited amplifier (JPC), two circulators and three insulators are used according to the state of the art.This corresponds to a volume of at least 191.1 cm³. 3 and a mass of at least 1.5 kg (and this mass comes only from the circulators and insulators). The volume calculation does not include the mass of the copper supports used for thermalization. In contrast, embodiments provide a structure with one output line and one (optional) circulator / insulator.

[0015] The characters are Fig. 1 a schematic representation of an integrated control and readout circuit arrangement 100 , which illustrates the readout of superconducting qubits according to embodiments. Fig. Figure 2 is a schematic representation of the integrated control and readout circuit 100 , which illustrates the control of superconducting qubits according to embodiments. The systems in the Fig. 1 and Fig. 2 are identical and illustrate a difference in the mode of operation (i.e., reading the qubits versus driving the qubits) of the circuits. 100 . The Fig. 1 and Fig. 2 (together with Fig. 3) apply to qubit resonator systems operating in reflection mode, as is clear to a person skilled in the art.

[0016] The circuit 100 It can be implemented on a chip (on-chip) and / or on a printed circuit board and / or as an integrated circuit. For example, this could be the integrated control and readout circuit. 100 It's about a chip. The circuit 100is functionally related to quantum systems. A quantum system consists of a superconducting qubit coupled to a readout resonator, allowing the superconducting qubit to be driven (i.e., driven into an excited state or a superposition of ground and excited states) and read out. The state of the qubit is read out by measuring the readout resonator. There are qubit-resonator systems... 102_1 until 102_N , where N corresponds to the last number of qubit resonator systems. Each qubit resonator system 102_1 until 102_N It has its own superconducting qubit, which is coupled to a readout resonator. For example, qubit-resonator systems... 102_1 until 102_N each superconducting qubit 154_1 until 154_N and each a readout resonator 152_1 until 152_NAs mentioned previously, readout resonators can be implemented as resonators made of discrete elements, resonators with microstrip / bandlines, resonators with coplanar waveguides, 3D microwave cavities, etc.

[0017] The integrated control and readout circuit 100 includes broadband directional coupler 104_1 until 104_N , which are functionally similar to the qubit resonator systems 102_1 until 102_N are connected. The circuit 100 contains diplexer 106_1 until 106_N , which are functionally compatible with the broadband directional couplers 104_1 until 104_N are connected. A signal combiner 108 is functionally compatible with each of the diplexers 106_1 until 106_N connected, so that the signal combiner 108 Inputs from the diplexers 106_1 until 106_N receives. Optionally, the circuit can be... 100 a broadband quantum-limited directional amplifier110 included, whose input is functionally connected to the output of the signal combiner 108 is connected. Optionally, the circuit can be 100 a broadband on-chip circulator with four ports 112 or include a broadband isolator connected to the output of the broadband quantum-limited directional amplifier. 110 is connected. The broadband quantum-limited directional amplifier 110 and the broadband on-chip circulator with four ports 112 can optionally be on-chip, i.e., on the chip / on the circuit 100 or be off-chip. Fig. 3 is an example of the broadband quantum-limited directional amplifier 110 and the broadband on-chip circulator with four ports 112 , which lies outside the chip.

[0018] According to embodiments, the scalable qubit control and readout circuit 100used to implement a range of quantum electrodynamic circuit systems (such as superconducting cavity / readout resonator qubit systems). 102_1 until 102_N ) to control and measure, which are controlled and measured in reflection mode. The superconducting cavity / readout resonator qubit systems 102_1 until 102_N The diagrams are shown for illustrative purposes. It should be noted that this drive and readout circuit is not limited to superconducting qubits. It can be used with any type of qubit coupled to microwave resonators (i.e., in all quantum systems). One condition is that the qubit drive signals and the readout signal are fed to the same terminal of the quantum system.

[0019] Now, let's look more closely at the components of the circuit arrangement. 100 , the broadband directional couplers 104_1 until 104_Nhave a frequency band that covers the frequency range of both qubits (i.e., qubits) 154 and selection resonators 152 ) covers (i.e., includes). The broadband directional couplers 104_1 until 104_N are units with four ports with the ports 103A , 103B , 103C and 103D Couplers are configured to couple a defined amount of electromagnetic power of a signal from one terminal to another, allowing the signal to be used in a different circuit. Only the directional coupler 104_1 is connected to the 103A until 103D This is done to ensure the figures remain clear. However, it should be noted that the other directional couplers 104_2 until 104_N They have the same connections as the directional coupler. 104_1function, whose connections are labelled for better understanding.

[0020] The control and readout signals are transmitted via the coupled connection. 103A the directional coupler 104_1 until 104_N supplied. The isolated connection 103D of the directional coupler 104_2 until 104_N It is terminated by a 50-ohm (Ω) termination element. This 50-ohm (Ω) termination element can be an on-chip termination element or an external 50-ohm termination element. 50 The -Ω termination element can be a load, for example a resistive load. The input terminal 103B of the directional coupler 104_1 until 104_N is with the qubit readout resonator systems 102_1 until 102_N connected. The attenuation of the signals (control signals and / or readout signals) coming from the coupled port 103A to the input connection 103BThe coupling noise level is between 10 and 30 decibels (dB).

[0021] The output port 103C of the directional coupler 104_1 until 104_N is with the on-chip diplexers 106_1 until 106_2 connected. The purpose of the diplexers 106_1 until 106_2 The process involves directing the reflected qubit pulses (i.e., reflected drive signals) to the 50 Ω termination element (on-chip or external) so that the reflected qubit pulses are extracted, while the reflected readout signals are routed to the output line / chain (OUT). The various readout signals, which the different diplexers... 106_1 until 106_N They are processed using the signal combiner. 108 linked to quantum signals (i.e., the reflected readout signals), and the signal combiner 108uses frequency-division multiplexing to combine the different (reflected) readout signals on a single transmission line, which operates at the frequencies f1 , f2 ,... f N Readout signals are generated. The readout signals can be connected in series, parallel, or in any combination. The various linked readout signals at the frequencies f1 , f2 ,... f N are from the signal combiner 108 to the broadband directional amplifier 110 Issued. The broadband directional amplifier 110 amplifies the linked readout signals at the frequencies f1 , f2 ,... f N The broadband directional amplifier 110 can an on-chip circulator 112 or insulator, which the quantum systems (such as the qubit cavity / readout resonator systems) follow. 102_1 until 102_N ) protects against noise from the output chain (i.e., OUT). The on-chip circulator 112or isolator can be implemented with three-wave mixing units (e.g. parametric Josephson converters) and hybrids or using ferrites and permanent magnets.

[0022] As an example of controlling a qubit resonator of Fig. Section 2 explains the following scenario for controlling the qubit resonator system. 102_1 with the readout resonator 152_1 and the superconducting qubit 154_1 However, the same applies analogously to controlling the qubit resonator system. 102_2 until 102_N with the selection resonators 152_2 until 152_N or the superconducting qubit 154_N The qubit resonator system 102_1 , the directional coupler 104_1 and the diplexer 106_1 They are all in a one-to-one relationship.

[0023] Each of the qubit resonator systems 102_1 until 102_N can be addressed simultaneously, almost simultaneously, and / or sequentially. Each of the qubits154_1 until 154_N Each qubit has its resonant frequency, which can be called the qubit frequency or qubit resonant frequency. For example, the qubits 154_1 until 154_N the qubit resonant frequencies f q1 until f qN , where N the last number. These frequencies can be the same or different (i.e., close together, e.g., separated by a few megahertz, or far apart, e.g., separated by a few hundred megahertz), depending on the specific implementation scheme of the quantum processor. In the example scenario for driving the qubit resonator system 102_1 has the qubit 154_1 the qubit resonance frequency f q1 Accordingly, a (control) microwave signal (tone) is generated at the frequency f q1 into the coupling connection 103A of the broadband directional coupler 104_1 entered to enter the qubit 154_1to bring / manipulate it into the desired state. The broadband directional coupler 104_1 couples a portion of the microwave drive signal (e.g., 1%) to the frequency f q1 to the connection 103B of the broadband directional coupler 104_1 and transmits the remainder (or almost the entire remainder) of the microwave control signal. f q1 at the isolated connection 103D (which is connected to a 50-Ω cold-terminating element). The drive microwave signal at the frequency f q1 is integrated into the qubit resonator system 102_1 entered and causes the qubit 154_1 oscillates because the control microwave signal is at the frequency f q1 the qubit resonance frequency f q1 of the qubit 154_1 corresponds to or nearly corresponds to the reflected microwave signal with the frequency f q1 from the qubit resonator system 102_1 enters the input port 103B of the broadband directional coupler 104_1one, and the majority of the signal (e.g. 99%) enters through the connection 103C out. The broadband directional coupler 104_1 is configured to convert the reflected (drive) microwave signal to the frequency f q1 to the common connection 105A of the diplexer 106_1 outputs. The diplexer 106_1 (together with the diplexers) 106_2 until 106_N ) has a low-pass filter that is connected to the terminal 105B is connected, and a high-pass filter is attached to the connection 105C is connected. The low-pass filter is designed to filter the reflected drive microwave signal at the frequency f q1 to the connection 105B forwards, so that the reflected control microwave signal is transmitted at the frequency f q1 derived through the 50 Ω cold termination element. The various qubit resonant frequencies are typically located... f q1 until f qN for the respective qubits154_1 until 154_N in the frequency range of approximately 3.5 to 5.5 gigahertz (GHz). Accordingly, the microwave signals for the control signal and the corresponding reflected microwave signals for the control signal (at the qubits) are located in this range. 154_1 until 154_N ) in the frequency range of approximately 3.5 to 5.5 gigahertz (GHz). The low-pass filter in each of the diplexers 106_1 until 106_N is designed to reflect the microwave signals of the control at the qubit resonance frequencies f q1 until f qN for the respective qubits 154_1 until 154_N allows through, so that none of the qubit resonant frequencies f q1 until f qN for the respective qubits 154_1 until 154_N the signal combiner 108This is achieved. In some implementations, the low-pass filters may be designed to allow frequencies below 5.6 GHz to pass, thus allowing the qubit frequencies in the frequency range of approximately 3.5 to 5.5 GHz to pass. In other implementations, the qubit resonant frequencies... f q1 until f qN For frequencies below 5.0 GHz, the low-pass filters can be designed to block frequencies below 5 GHz from reaching the connection. 105B conduct to the 50-Ω cold termination element.

[0024] When the reflected drive microwave signals are at qubit resonance frequencies f q1 until f qN not through the diplexer 106_1 until 106_N derived, the signal combiner would 108 the qubit resonant frequencies f q1 until f qN reject them, and therefore these rejected signals would return to the qubit resonator system. 102_1 until 102_Nbe reflected. This is an undesirable situation and is avoided by using a low-pass filter at the connection. 105B and the high-pass filter at the connection 105C are planned, which are the qubit resonant frequencies f q1 until f qN reject.

[0025] With the diplexers 106_1 until 106_N These are units with 3 connections. 105A , 105B and 105C Only the diplexer 106_1 is connected to the 105A until 105C This is a term used to maintain clarity regarding the figures. However, it should be noted that the other diplexers 106_2 until 106_N They have the same connections and are operated in the same way as the diplexer. 106_1 , whose connections are labelled.

[0026] In the exemplary scenario of addressing the qubit 154_1 in the qubit resonator system 102_1The reflected control microwave signal was measured at the frequency f q1 derived, and the addressing of the qubit 154_1 in the qubit resonator system 102_1 is finished. The same control process used for the qubit 154_1 in the qubit resonator system 102_1 As discussed, this applies to addressing the qubits. 154_2 until 154_N in the qubit resonator system 102_2 until 102_N , however, with the respective qubit resonance frequencies f q2 until f qN and the respective entrance management.

[0027] As an example of reading out a qubit resonator in Fig. 1 explains the following scenario: reading out the qubit resonator system 102_1 with the readout resonator 152_1 and the superconducting qubit 154_1 However, the same applies analogously to reading out the qubit resonator systems. 102_2 until 102_N with the selection resonators 152_2 until 152_Nor the superconducting qubits 154_2 until 154_N The state of each of the qubits 154_1 until 154_N can be read out simultaneously or almost simultaneously by using the respective readout resonators 152_1 until 152_N be read out. Each of the readout resonators 152_1 until 152_N It has its own resonant frequency, which can be called the readout resonator frequency or readout resonator resonance frequency. For example, the readout resonators 152_1 until 152_N (Different) readout resonator resonance frequencies f1 until f N , where N the last number. In the exemplary scenario of reading the readout resonator 152_1 in the qubit resonator system 102_1 has the selection resonator 152_1 the readout resonator resonance frequency f1 Accordingly, a (readout) microwave signal (audio signal) is generated at the frequency f1into the coupling connection 103A of the broadband directional coupler 104_1 entered to select the readout resonator 152_1 to read out. The broadband directional coupler 104_1 couples a portion of the microwave readout signal at f1 to the connection 103B of the broadband directional coupler 104_1 and transmits the remainder (or almost the entire remainder) of the readout signal at the frequency f1 at the isolated connection 103D from (which is connected to a 50-Ω cold-terminating element). The read microwave signal with the frequency f1 is integrated into the qubit resonator system 102_1 entered. At this point, the process for inputting the drive microwave signal and the readout microwave signal is the same. The readout microwave signal with the frequency f1 , which is part of the qubit resonator system 102_1 However, what is entered causes the readout resonator to... 152_1oscillates because the read microwave signal has a frequency of f1 with the readout resonator resonance frequency f1 of the readout resonator 152_1 matches or nearly matches it. By matching the read microwave signal with the frequency f1 with the readout resonator 152_1 Being in resonance causes the selection resonator to activate. 152_1 , a reflected (readout resonator) microwave signal with the frequency f1 to transmit. The reflected, read-out microwave signal with the frequency f1 is from the qubit resonator system 102_1 back to the input port 103B of the broadband directional coupler 104_1 Issued. The broadband directional coupler 104_1 is configured to capture most of the reflected read-out microwave signal at the frequency f1 to the output port 103C of the directional coupler 104_1and then to the common connection 105A of the diplexer 106_1 outputs. The diplexer 106_1 (together with the diplexers) 106_2 until 106_N ) has the low-pass filter at the connection 105B and the high-pass filter at the connection 105C The high-pass filter is designed to filter the reflected readout resonator microwave signal at the frequency f1 via the connection 105C for connection 107_1 of the signal combiner 108 conducts, while the reflected qubit microwave signal is carried at the frequency f1 is blocked. The different readout resonant frequencies are usually located at... f1 until f N for the respective readout resonator 152_1 until 152_N in the frequency range of approximately 6 GHz or higher. The readout resonators 152_1 until 152_NThey are designed to have different resonant frequencies. The high-pass filter in each of the diplexers 106_1 until 106_N is designed in such a way that it reads out the respective reflected microwave signals at the read-out resonant frequencies. f1 until f N for the respective selected resonators 152_1 until 152_N allows each of the selected resonant frequencies to pass through. f1 until f N for the selection resonators 152_1 until 152_N the signal combiner 108 to achieve this. For example, the high-pass filters can be designed to allow frequencies above 6 GHz to pass through.

[0028] Exemplary details of the diplexers 106_1 until 106_N were illustrated for clarification, but the implementation of the diplexers 106_1 until 106_N should not be restricted. The diplexers must therefore be used. 106_1 until 106_NThey don't necessarily need to use a low-pass filter and a high-pass filter. In other implementations, the diplexers can... 106_1 until 106_N Use bandpass filters, where a bandpass filter operating in the qubit frequency range ( f q1 until f qN ) transmits, at the connection 105B is connected and a wide bandpass filter, which operates in the range of the readout frequencies ( f1 until f N ) transmits, is connected to 105C.

[0029] In the exemplary scenario of the readout resonator 152_1 in the qubit resonator system 102_1 The reflected readout microwave signal was measured at the frequency f1 into the connection 107_1 of the signal combiner 108 entered. The signal combiner 108 is configured to convert the microwave signal to the frequency f1 from the selection resonator 152_1 with the read-out microwave signals at the frequency f2 untilf N from the selection resonators 152_2 until 152_N (which also have connections) 107_2 until 107_N (were entered) linked. The linked reflected microwave signals at the frequencies f1 until f N will then be disconnected 109 of the signal combiner 108 to the broadband quantum-limited directional amplifier 110 output. The amplifier 110 is configured to convert the linked reflected microwave signal of the frequencies f1 until f N amplified. The amplifier 110 was designed to amplify within a bandwidth that covers the readout frequencies f1 until f N covers. The amplified microwave signals of the frequencies f1 until f N are connected to a broadband circulator 112 output, which displays the linked reflected microwave signals of the frequencies f1 until f N to one with OUT forwards the designated transmission line.

[0030] The same readout process used for the readout resonator 152_1 in the qubit resonator system 102_1 As explained above, this applies to the reading of the readout resonators. 152_2 until 152_N in the qubit resonator system 102_2 until 102_N , however, with the corresponding readout resonance frequencies f2 until f N .

[0031] The integrated control and readout circuit 100 Depending on the design, it offers many advantages. The circuit 100 can be fully integrated onto a single chip or printed circuit board. The circuit 100 minimizes the number of output lines ( OUT ) and control lines. One control line for the quantum-limited amplifier. 110 would only be necessary if the quantum-limited amplifier 110 on the chip 100 would be located, and Fig. Figure 3 illustrates an example where the quantum-limited amplifier 110 not on the chip 100 All components are passive and do not require any control lines carrying drive or control signals, except for the directional amplifier (i.e., the quantum-limited amplifier). 100 ) and the on-chip circulator / isolator (e.g., circulator) 112 The control and readout technology with the circuit 100 This integrated circuit requires no off-chip circulators or isolators. 100 can be thermally treated well, since the circuit 100 It does not require a large number of circulators / isolators, as would be necessary according to the state of the art. For example, the state-of-the-art high-fidelity measurement method requires one for each of the N-qubit resonator systems. 102Two circulators (when using a parametric Josephson amplifier in the output chain) and three isolators per qubit resonator system. Accordingly, the technique can be implemented using the circuit 100 In their various embodiments, they exhibit lower mass and a smaller footprint than prior art approaches that incorporate commercial cryogenic circulators and insulators. Furthermore, the circuit can 100 They must exhibit low insertion loss, e.g., less than 2 decibels (dB), as this can be achieved with superconducting circuits or very low-loss normal metal and dielectric components. The required low loss is necessary to minimize the loss of quantum information in the output chain.

[0032] Fig. Figure 3 is a schematic representation of an integrated control and readout circuit arrangement. 100 according to embodiments. In Fig. 3 are on the integrated circuit 100 Fewer switching elements are shown than in the Fig. 1 and Fig. 2. Fig. Figure 3 illustrates the integrated circuit 100 with the broadband directional couplers 104_1 until 104_N , the diplexers 106_1 until 106_N and the signal combiner 108 In Fig. Three components are missing from the chip of the quantum-limited directional amplifier. 110 and the circulator 112 . Fig. Figure 3 illustrates an example using a quantum processor. 300 , which is functionally compatible with the integrated circuit 100 is connected. The control and read function in Fig. 3 is identical to the one in the Fig. 1 and Fig. 2 described function.

[0033] Fig. Figure 4 is a schematic representation of the signal combiner. 108for combining quantum signals (i.e., microwave signals) according to embodiments. The signal combiner 108 It is configured to use frequency division multiplexing to assign different frequencies to different microwave signals on a single output transmission line. The signal combiner 108 contains bandpass microwave filters, commonly known as bandpass filters 405 The various bandpass filters 405 are used as bandpass filters 405_1 up to bandpass filter 405_N shown. Each bandpass filter 405 It has a different narrow passband through which microwave signals with a frequency within that narrow passband are transmitted (i.e., passed through) and signals with a frequency outside that narrow passband are reflected (i.e., blocked). The bandpass filter 405_1 has its own narrow passband with the bandwidth 1 ( BW1 ), the bandpass filter 405_2 has its own narrow passband with the bandwidth 2 ( BW2 ), and the bandpass filter 405_N has its own narrow passband with the bandwidth N ( BW N ).

[0034] For example, the bandpass filter 405_1 configured with a passband (frequency band) such that a (reflected readout) microwave signal 305_1 with the frequency f1 (corresponding to the selection resonator) 152_1 ) is passed through (transmitted), while all other microwave signals are blocked. 305_2 until 305_N with the frequencies f2 until f N , which are outside the passband for the bandpass filter 405_1 The sound waves are blocked (reflected). Similarly, the bandpass filter... 405_2 configured with a passband (frequency band) to allow a (reflected readout) microwave signal 305_2with the frequency f2 (corresponding to the selection resonator) 152_2 ) is passed through (transmitted), while all other microwave signals are blocked. 305_1 , 305_3 until 305_N with the frequencies f1 , f3 until f N , which are outside the passband for the bandpass filter 405_2 The frequencies are blocked (reflected). Similarly, the bandpass filter... 405_N configured with a passband (frequency band) such that a (reflected readout) microwave signal 305_N with the frequency f N (corresponding to the selection resonator) 152_N ) is passed through (transmitted), but all other microwave signals are not. 305_1 until 305_N -1 with the frequencies f1 until f N-1 , which are outside the passband for the bandpass filter 405_N lie, be blocked (reflected). The microwave signals 305_1 until 305_N are generally referred to as microwave signals 305This is referred to as qubit resonator quantum systems. 102_1 until 102_N functionally compatible with the signal combiner 108 are connected, the microwave signals 305 at the respective frequencies f1 until f N are located which are intended for reading out qubits (via readout resonators or cavities), as is clear to a person skilled in the art.

[0035] The signal combiner 108 includes the connections 107_1 until 107_N , which are individually connected to the respective bandpass filters 405_1 until 405_N are connected. In the signal combiner 108 is the connection 107_1 with the bandpass filter 405_1 , the connection 107_2 with the bandpass filter 405_2 and the connection 107_N with the bandpass filter 405_N connected. Every connection 107_1 until 107_N is with an end of its own bandpass filters 405_1 up to bandpass filter 405_Nconnected. The other end of the bandpass filter 405_1 until 405_N is via a common node 415 with a common connection 109 connected. The common node 415 A common connection point, a common transmission line, a common conductor, etc., can serve as the common location for the electrical connection. The common connection 109 is with every bandpass filter 405_1 up to bandpass filter 405_N connected, while the individual connections 107_1 until 107_N (only) with their respective bandpass filters 405_1 up to bandpass filter 405_N are connected.

[0036] Since the bandpass filters 405_1 until 405_N only reflected readout microwave signals 305_1 until 305_N transmitted in the respective passband, the signal combiner 108 configured so that each bandpass filter 405_1up to bandpass filter 405_N covers a different frequency band (or sub-band), so that none of the passbands (the bandpass filter) 405 ) overlaps. Accordingly, each connection 107_1 until connection 107_N isolated from each other because each has its own bandpass filter 405_1 until 405_N is connected so that no microwave signal 305 through a connection 107 via the common node 415 into another connection 107 reached. Thus, every connection 107 from other connections 107 isolated and designed to generate its own microwave signal 305 transmits at a predefined frequency (or within a predefined frequency band), since it uses its own bandpass filter 405 is connected. Accordingly, the bandpass filters are 405_1 until 405_N for providing isolation between the terminals 107- 1 until 107_N responsible.

[0037] The respective connections 107 , bandpass filter 405 , the common node 415 and the common connection 109 are via transmission lines 30 interconnected. The transmission line 30 It can be a stripline, a microstripline, a coplanar waveguide, etc. Microwave bandpass filters 405Bandpass filters are designed and implemented using lossless or low-loss lumped elements such as superconducting inductors, superconducting gap capacitors and / or plate capacitors, and passive superconducting elements. Superconducting elements include lumped-element inductors, meandering lines, kinetic inductor lines, gap capacitors, interlocking (interdigital) capacitors, and / or plate capacitors (with low-loss dielectrics). Other possible implementations of bandpass filters include coupled line filters and / or capacitively coupled series resonators.

[0038] The signal combiner 108 is with the frequency ratio f1 < f2 < ...< f N configured, with each frequency f1 , f2 , ... f N the center frequency of the bandpass filters 405_1 until 405_N is. The signal combiner 108is configured to satisfy the following inequality B W j + B W i 2 < | f j − f i | where i, j = 1, 2, ...N and j ≠ i. This inequality requires that the frequency spacing between the center frequencies of each pair of bandpass filters exceeds their average bandwidths. In other words, the inequality ensures that none of the bandpass filters have overlapping bandwidths (i.e., frequency ranges). For example, a bandpass filter 405 have a passband of 1 megahertz (MHz), another bandpass filter 405 can have a passband of 10 MHz, another bandpass filter 405 can have a passband of 100 MHz, etc.

[0039] Fig. Figure 5 is a schematic representation of the signal combiner. 108 for quantum signals according to embodiments. The signal combiner 108It contains all the features described herein. In addition, the signal combiner contains 108 Additional features to ensure impedance matching for the transmission of microwave signals (i.e., to minimize reflections along the signal path) and also the connection of multiple branches / lines to the common node. 415 to enable.

[0040] In Fig. 5 are impedance converters 505_1 until 505_N each between the respective connections 107_1 until 107_N and their associated bandpass filters 405_1 until 405_N added. The signal combiner also contains 108 a broadband impedance converter 510 , which is connected to the common node 415 and the joint connection 109 is connected. The impedance converters 505_1 until 505_N and the impedance converter 510are configured to provide impedance matching. At one end of the signal combiner 108 are the impedance converters 505_1 until 505_N so formed that they match the input impedance Z0 the connections 107_1 until 107_N correspond (or nearly correspond) to the bandpass filter 405_1 until 405_N correspond to the assigned characteristic impedance. Each of the impedance converters 505_1 until 505_N is with a characteristic impedance Z=V( Z0 Z H ) configured, whereby Z0 the input impedance (as well as the output impedance) is, where Z H the high impedance of the bandpass filters 405_1 until 405_N is and where Z is the impedance of the individual impedance converters 505_1 until 505_N The mean characteristic impedance Z is the square root of the product of Z0 and Z H Each of the converters for impedance matching505_1 until 505_N has a length corresponding to its own respective relationship λ1 / 4 , λ2 / 4 ,..., l N / 4, where λ1 the wavelength of the microwave signal 305_1 is, λ2 the wavelength of the microwave signal 305_2 is and l N the wavelength of the microwave signal 305_N These impedance converters generally have low bandwidths. One reason why converting the impedance of the unit connections is Z0 the high characteristic impedance Z H One advantage of using a common node is that, generally, high-impedance transmission lines, such as microstrip or stripline transmission lines, have narrow signal lines. This minimizes the physical size of the common node and allows more lines to be connected at that node. This is particularly relevant when the bandpass filters are implemented as coupled line filters and / or capacitively coupled resonators. However, if all bandpass filters are implemented with lumped elements (with a very small footprint), such impedance transformations may be less necessary.

[0041] In one implementation, the impedance converters can 505_1 until 505_N impedance-matched transmission lines, i.e., those that are conical, with one end having a large width that matches the input impedance Z0is adapted, and the opposite end has a small width, which is adapted to the high impedance Z H the bandpass filter 405 is adapted.

[0042] In one implementation, the broadband impedance converter can be 510 This involves an impedance-matched transmission line, where one end has a narrow width to accommodate the high impedance. Z H the bandpass filter 405 (via the common node) 415 ) is adapted, while the other end has a large width that is adapted to the output impedance Z0 is adapted. Such a broadband impedance converter 510This can be implemented using conical transmission lines, e.g., transmission lines whose width is adiabatically varied on the scale of the maximum signal wavelength. Other implementations of conical lines known to a person skilled in the art are also possible, e.g., the exponential cone or the Klopfenstein cone. Furthermore, it should be noted that the broadband requirement for this impedance converter is lower compared to other converters. 505 This results in the fact that this broadband converter 510 It must adapt the characteristic impedance for a wide range of signal frequencies transmitted via it, unlike impedance converters. 505 , which only need to adjust the impedance for a narrow frequency range centered around the corresponding center frequency of the respective bandpass.

[0043] Fig. Figure 5 illustrates a specific example of impedance matching, and it should be noted that the general scheme of the combiner 108 is not limited to this specific implementation. For example, in some implementations the bandpass filters 405 the same characteristic impedance as the connection Z0 ( 107 ) exhibit, and impedance converters are used between the bandpass filters. 405 and the high impedance Z H built-in, which is connected to the common node 109 is connected.

[0044] The impedance designation Z0 is the characteristic impedance at the terminals 107_1 until 107_N and at the connection 109 (These can be the input and output ports). For example, at each of the ports 107 and 109 the characteristic impedance Z0 50 ohms (Ω), as is clear to any expert.

[0045] It should be noted that N The last of the frequencies, microwave signals 305 , bandpass filter 405 and impedance converter 505_N represents. Furthermore, represents N the last of qubit resonator systems 102 , Selector resonators 152 , Qubits 154 , directional couplers 104 , diplexers 106 etc.

[0046] The circuit elements of the circuit 100 can be made of superconducting material. The respective connections 107 , bandpass filter 405 , the common node 415 , the common connection 109 , the impedance converter 505 and the transmission lines 30 are made of superconducting materials. Furthermore, the qubit resonator systems are 102 , Selector resonators 152 , Qubits 154 , directional coupler 104 , Diplexer 106 , the amplifier 110and the circulator 112 Made from superconducting materials. Examples of superconducting materials (at low temperatures such as 10 to 100 millikelvin (mK) or about 4 K) are niobium, aluminum, tantalum, etc. For example, Josephson junctions are made of superconducting material, and their tunnel junctions may consist of a thin tunnel barrier such as an oxide. The capacitors may be made of superconducting material separated by low-loss dielectric material. The transmission lines (i.e., conductors) connecting the various elements are made of a superconducting material.

[0047] Fig. 6 is a schedule 600 a method for forming an integrated control and readout circuit / assembly 100 according to embodiments. The method involves providing directional couplers. 104_1 until 104_N, which are configured to work with the qubit resonator systems 102_1 until 102_N in the block 602 to be connected, connecting diplexers 106_1 with the directional couplers 104_1 until 104_N in the block 604 and connecting a microwave signal combiner 108 with each of the diplexers 106_1 until 106_N in the block 606 .

[0048] Each of the directional couplers 104_1 until 104_N It contains a first connection, a second connection, a third connection, and a fourth connection. The first connection 103A is configured to receive a qubit signal and a readout signal; the second connection 103B can be used with qubit resonator systems 102_1 until 102_N to be connected, the third connection 103C can be used with the diplexers 106_1 until 106_N to be connected, and the fourth connection 103Dis an isolated connection.

[0049] The diplexers 106_1 until 106_N Each contains a low-pass filter connection 105B , a high-pass filter connection 105C and a common connection (C) 105A The common connector is configured to support both low and high frequency bands, corresponding to the low-pass and high-pass band connectors, respectively. 105A the diplexer 106_1 until 106_N is with the directional couplers 104_1 until 104_N tied together.

[0050] The diplexers 106_1 until 106_N are configured to send a reflected drive microwave signal to the low-pass filter port 105B guide to where the low-pass filter connection 105B is connected to a termination point (e.g., a 50-Ω termination element). The high-pass filter connection 105C is with the signal combiner108 connected. The microwave signal combiner 108 is configured to receive microwave signals from each of the diplexers 106_1 until 106_N linked, as in Fig. 1 shown. The microwave signal combiner 108 is configured to process linked microwave signals (e.g., linked microwave signals with the frequencies f1 until f N ) to a quantum-limited amplifier 110 outputs. The quantum-limited amplifier 110 is configured to amplify the linked microwave signals and send the linked microwave signals to a circulator 112 spends.

[0051] Fig. 7 is a schedule 700 a method for controlling qubit resonator systems 102_1 until 102_N according to embodiments. The method involves transmitting (drive) microwave signals (at the qubit resonant frequencies). f q1 untilf qN ) to the qubit resonator systems 102_1 until 102_N through directional couplers 104_1 until 104_N (in block 702 ), received by the directional couplers 104_1 until 104_N , from reflected (drive) microwave signals (at the qubit resonance frequencies) f q1 until f qN ) from the qubit resonator systems 102_1 until 102_N (in block 704 ) and receiving the transmitted (control) microwave signals from the directional couplers 104_1 until 104_N (in block 706 ) through the diplexers 106_1 until 106_N In other words, those from the qubit resonator systems 102_1 until 102_N reflected signals are processed by the directional coupler. 104_1 until 104_N transmitted. The diplexers 106_1 until 106_N are configured to reflect the (drive) microwave signals (at the qubit resonant frequencies) f q1 untilf qN ) to a final connection (e.g. 50-Ω cold termination element).

[0052] Fig. 8 is a schedule 800 a method for reading out qubit resonator systems (i.e., deriving the state of the superconducting qubits) 154_1 until 154_N by reading the readout resonators 152_1 until 152_N ) according to embodiments. The method involves transmitting (readout) microwave signals (at the readout resonant frequencies). f1 until f N ) to the qubit resonator systems 102_1 until 102_N (in block 802 ) and receiving reflected (readout) microwave signals (at the readout resonant frequencies) f1 until f N ) from the qubit resonator systems 102_1 until 102_N (in block 804 ) through directional coupler 104_1 until 104_NFurthermore, the procedure includes receiving the transmitted readout microwave signals (at the readout resonant frequencies). f1 until f N ) through the directional couplers 104_1 until 104_N (in block 806 ) and receiving the transmitted readout microwave signals (at the readout resonant frequencies) f1 until f N ) by the microwave signal combiner 108 from the diplexers 106_1 until 106_N (in block 808 It should be noted that the transmitted readout microwave signals (at the readout resonant frequencies) f1 until f N ) previously from the qubit resonator systems 102_1 until 102_N These were reflected (readout) microwave signals.

[0053] The microwave signal combiner 108 is configured to convert the multiple transmitted microwave signals into multiple microwave signals (at the readout frequencies) f1 untilf N ) linked. Furthermore, the method includes transmitting the linked readout microwave signals (with the readout resonance frequencies). f1 until f N ) by the microwave signal combiner 108 to a quantum-limited amplifier 110 (in block 810 ).

[0054] The technical effects and advantages include methods and structures for a scalable qubit drive and readout circuit. These structures can be fully integrated on a single chip or printed circuit board. Technical advantages include minimizing the number of output and control lines. Furthermore, the technical effects and advantages include a structure with lower mass, improved thermal management, and a smaller footprint compared to systems incorporating commercial cryogenic circulators and isolators.

[0055] The term "approximately" and variations thereof are intended to include the degree of error in measuring the specified quantity based on the equipment available at the time the application was filed. For example, "approximately" may include a range of ± 8%, 5%, or 2% of a given quantity.

[0056] The flowcharts and block diagrams or charts in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this context, each block in the flowcharts or block diagrams or charts can represent a module, segment, or part of instructions that includes one or more executable instructions for performing the specific logical function(s). In some alternative embodiments, the functions specified in the block may occur in a different order than shown in the figures. For example, two blocks shown consecutively may in reality be executed essentially simultaneously, or the blocks may sometimes be executed in reverse order depending on the corresponding functionality.It should also be noted that each block of the block diagrams or charts and / or flowcharts, as well as combinations of blocks in the block diagrams or charts and / or flowcharts, can be implemented by special hardware-based systems that perform the specified functions or steps, or execute combinations of special hardware and computer instructions.

[0057] The descriptions of the various embodiments of the present invention are provided for illustrative purposes; however, they are not intended to be exhaustive or limiting for the embodiments described. Many modifications and variations will be obvious to a person skilled in the art without deviating from the scope of the described embodiments. The terminology used here has been chosen to best explain the basic concepts of the embodiments, their practical application, or technical improvements over technologies available on the market, or to enable other persons skilled in the art to understand the embodiments described herein.

Claims

[1] Integrated control and readout circuit arrangement, wherein the arrangement comprises: Directional couplers configured to connect to qubit resonator systems; Diplexers connected to the directional couplers; and a microwave signal combiner connected to the diplexers. [2] Arrangement according to claim 1, wherein each of the directional couplers includes a first terminal, a second terminal, a third terminal and a fourth terminal. [3] Arrangement according to claim 2, wherein the first connection is configured to receive a qubit signal and a readout signal, the second connection is connectable to the qubit resonator systems, the third connection is connectable to the diplexers and the fourth connection is an isolated connection. [4] Arrangement according to one of the preceding claims, wherein the diplexers comprise a low-pass band port, a high-pass band port and a common port, the common port being configured to support both low-frequency and high-frequency bands belonging to the low-pass band port and the high-pass band port, respectively. [5] Arrangement according to claim 4, wherein the common connection of the diplexers is connected to the directional couplers. [6] Arrangement according to claim 4 or 5, wherein the diplexers are configured to direct a reflected drive microwave signal to the low-pass band port, the low-pass band port being connected to a termination. [7] Arrangement according to one of claims 4 to 6, wherein the high-pass band connection is connected to the microwave signal combiner. [8] Arrangement according to one of the preceding claims, wherein the microwave signal combiner is configured to combine microwave signals from the diplexers. [9] Arrangement according to a preceding claim, wherein the microwave signal combiner is configured to output linked microwave signals to a quantum-limited amplifier. [10] Arrangement according to claim 9, wherein the quantum-limited amplifier is configured to amplify the linked microwave signals and output the amplified linked microwave signals to a circulator. [11] Method for forming an integrated control and readout circuit arrangement, wherein the method comprises: Providing directional couplers configured to connect to qubit resonator systems; Connecting diplexers to the directional couplers; and Connecting a microwave signal combiner to the diplexers. [12] Method according to claim 11, wherein each of the directional couplers includes a first terminal, a second terminal, a third terminal and a fourth terminal. [13] Method according to claim 12, wherein the first connection is configured to receive a qubit signal and a readout signal, the second connection is connectable to the qubit resonator systems, the third connection is connectable to the diplexers and the fourth connection is an isolated connection. [14] Method according to any one of claims 11 to 13, wherein the diplexers include a low-pass band port, a high-pass band port and a common port, wherein the common port is configured to support both low-frequency and high-frequency bands belonging to the low-pass band port and the high-pass band port, respectively. [15] Method according to claim 14, wherein the common connection of the diplexers is connected to the directional couplers. [16] Method according to claim 14 or 15, wherein the diplexers are configured to direct a reflected drive microwave signal to the low-pass band port, the low-pass band port being connected to a termination. [17] Method according to claim 14, 15 or 16, wherein the high-pass band connection is connected to the microwave signal combiner. [18] Method according to any one of claims 11 to 17, wherein the microwave signal combiner is configured to combine microwave signals from the diplexers. [19] Method according to any one of claims 11 to 18, wherein the microwave signal combiner is configured to output linked microwave signals to a quantum-limited amplifier. [20] Method according to claim 19, wherein the quantum-limited amplifier is configured to amplify the coupled microwave signals and output the coupled microwave signals that have been amplified to a circulator. [21] Chip comprising an integrated circuit arrangement live and random in any one of claims 1 to 10. [22] Chip according to claim 21, further comprising a quantum-limited amplifier connected to the microwave signal combiner. [23] Chip according to claim 22, further comprising an insulator connected to the quantum-limited amplifier. [24] Methods for driving qubit resonator systems: Sending microwave signals through the directional couplers to the qubit resonator systems; Receiving the microwave signals reflected back from the qubit resonator systems by the directional couplers; and Receiving the microwave signals from the directional couplers by the diplexers, the diplexers being configured to direct the microwave signals to a termination. [25] Method for reading out qubit resonator systems via an integrated drive and random circuit arrangement formed by a method according to any one of claims 11 to 20, wherein the method comprises: Sending microwave signals through the directional couplers to the qubit resonator systems; Receiving the microwave signals reflected back from the qubit resonator systems by the directional couplers; Receiving the microwave signals from the directional couplers by the diplexers; Receiving the microwave signals from the diplexers by the microwave signal combiner, wherein the microwave signal combiner is configured to combine the microwave signals into linked microwave signals; and Sending the combined microwave signals through the microwave signal combiner to a quantum-limited amplifier.