WO2018063168A1

WO2018063168A1 - On-chip frequency tuning of resonator structures in quantum circuits

Info

Publication number: WO2018063168A1
Application number: PCT/US2016/054039
Authority: WO
Inventors: Nicole K. THOMAS; James S. Clarke; Ravi Pillarisetty; Jeanette M. Roberts; Hubert C. GEORGE
Original assignee: Intel Corporation
Priority date: 2016-09-28
Filing date: 2016-09-28
Publication date: 2018-04-05

Abstract

Embodiments of the present disclosure provide a quantum device that includes qubits, at least one resonator, and a resonator tuning assembly, all housed on a single substrate or a single die. By implementing a resonator tuning assembly on the same die as the qubits and its resonator(s), the resonant frequency of the resonator can be controlled on-chip. In this manner, the resonant frequency can be fine-tuned to compensate for manufacturing variations or can be changed for any other purposes, as needed. Integration of means for varying the resonator frequency with the resonator and the qubits can greatly reduce complexity and lower the cost of quantum computing devices and provide an approach that can be efficiently used in large-scale manufacturing. Methods for fabricating such quantum devices are also disclosed.

Description

ON-CHIP FREQUENCY TUNING OF RESONATOR STRUCTURES IN QUANTUM CIRCUITS

Technical Field

[0001] This disclosure relates generally to the field of quantum computing, and more specifically, to providing on-chip resonant frequency control for resonator structures in quantum circuits.

Background

[0002] Quantum computing refers to the field of research related to computation systems that use quantum mechanical phenomena to manipulate data. These quantum mechanical phenomena, such as superposition (in which a quantum variable can simultaneously exist in multiple different states) and entanglement (in which multiple quantum variables have related states irrespective of the distance between them in space or time), do not have analogs in the world of classical computing, and thus cannot be implemented with classical computing devices.

Brief Description of the Drawings

[0003] To provide a more complete understanding of the present disclosure and features and advantages thereof, reference is made to the following description, taken in conjunction with the accompanying figures, wherein like reference numerals represent like parts, in which:

[0004] FIG. 1 provides a schematic illustration of an example quantum circuit, according to some embodiments of the present disclosure.

[0005] FIG. 2 provides a schematic illustration of an example quantum computing device that may include any of the integrated assemblies for providing on-chip resonant frequency control for resonator structures in quantum circuits described herein, according to some embodiments of the present disclosure.

[0006] FIG. 3 provides a schematic illustration of a magnetic field generated by a current-carrying wire, according to some embodiments of the present disclosure.

[0007] FIG. 4 provides a top-view schematic illustration of a portion of a quantum device where control of the resonant frequency of a resonator is implemented by providing a resonator tuning wire in the same plane as the resonator, according to some embodiments of the present disclosure.

[0008] FIG. 5 provides a top-view schematic illustration of a portion of a quantum device where control of the resonant frequency of a resonator is implemented by providing a resonator tuning wire in a plane that is below the plane of the resonator, according to some embodiments of the present disclosure.

[0009] FIG. 6 is a flow diagram of an illustrative method of manufacturing a quantum device, according to some embodiments of the present disclosure.

[0010] FIGs. 7-8 are flow diagrams of different illustrative methods of operating a quantum device, according to some embodiments of the present disclosure. Detailed Description

Overview

[0011] As previously described herein, quantum computing, or quantum information processing, refers to the field of research related to computation systems that use quantum-mechanical phenomena to manipulate data. One example of quantum-mechanical phenomena is the principle of quantum superposition, which asserts that any two or more quantum states can be added together, i.e.

superposed, to produce another valid quantum state, and that any quantum state can be represented as a sum of two or more other distinct states. Quantum entanglement is another example of quantum- mechanical phenomena. Entanglement refers to groups of particles being generated or interacting in such a way that the state of one particle becomes intertwined with that of the others. Furthermore, the quantum state of each particle cannot be described independently. Instead, the quantum state is given for the group of entangled particles as a whole. Yet another example of quantum-mechanical phenomena is sometimes described as a "collapse" because it asserts that when we observe (measure) particles, we unavoidably change their properties in that, once observed, the particles cease to be in a state of superposition or entanglement (i.e. by trying to ascertain anything about the particles, we collapse their state).

[0012] Put simply, superposition postulates that a given particle can be simultaneously in two states, entanglement postulates that two particles can be related in that they are able to instantly coordinate their states irrespective of the distance between them in space and time, and collapse postulates that when one observes a particle, one unavoidably changes the state of the particle and its' entanglement with other particles. These unique phenomena make manipulation of data in quantum computers significantly different from that of classical computers (i.e. computers that use phenomena of classical physics). Classical computers encode data into binary values, commonly referred to as bits. At any given time, a bit is always in only one of two states - it is either 0 or 1. Quantum computers use so- called quantum bits, referred to as qubits (both terms "bits" and "qubits" often interchangeably refer to the values that they hold as well as to the actual devices that store the values). Similar to a bit of a classical computer, at any given time, a qubit can be either 0 or 1. However, in contrast to a bit of a classical computer, a qubit can also be 0 and 1 at the same time, which is a result of superposition of quantum states. Entanglement also contributes to the unique nature of qubits in that input data to a quantum processor can be spread out among entangled qubits, allowing manipulation of that data to be spread out as well: providing input data to one qubit results in that data being shared to other qubits with which the first qubit is entangled.

[0013] Compared to well-established and thoroughly researched classical computers, quantum computing is still in its infancy, with the highest number of qubits in a solid-state quantum processor currently being about 10. One of the main challenges resides in protecting qubits from decoherence so that they can stay in their information-holding states long enough to perform the necessary calculations and read out the results. Qubits are often operated at cryogenic temperatures, typically just a few degrees Kelvin or even just a few millidegrees above absolute zero, because cryogenic temperatures are thought to help minimize qubit decoherence. Cryogenic temperature operation provides additional challenges to implementing larger arrays of qubits, partly because of the difficulties interfacing various external control devices and assemblies with qubits kept at some kind of cooling assemblies.

[0014] Quantum circuits implementing qubits use resonator structures to couple and read qubits, with the resonator structures provided on the same substrate with, and in the vicinity of, the qubits. In general, a resonator structure, often simply referred to as a "resonator," is a structure that can support oscillations within the structure (i.e. resonance). A frequency at which such oscillations occur is referred to as a "resonant frequency." By bringing frequencies of other items, such as e.g. qubits or readout lines in a quantum circuit, closer to or further away from the resonant frequency of a resonator, qubits can be coupled/decoupled and/or read.

[0015] A resonant frequency of a resonator may be defined by the original design. In other words, a resonator can be built to have a certain predefined resonant frequency, e.g. based on geometric and material properties. In some cases, a resonant frequency of a resonator may be controlled using magnetic fields created by external sources, e.g. by external magnets. Such magnetic field sources are "external" in a sense that, while qubits and resonators are provided on a chip kept at cryogenic temperatures, these sources are typically provided separately from the qubit chip and are kept at higher temperatures. While this may be suitable for implementing just a few qubits, there are several reasons why these approaches for setting resonant frequencies of resonators will face significant challenges with quantum circuit components that include increasingly larger number of qubits. One reason is that, as more and more qubits are implemented on a wafer, manufacturing variations across the wafer will likely come into play, resulting in deviations of resonant frequencies of various resonators from their desired values. At the same time, using external magnetic sources to control the resonant frequencies of various qubit resonators is not suitable for large-scale manufacturing of quantum computing devices.

[0016] Embodiments of the present disclosure provide a quantum device that includes qubits, at least one resonator, and a resonator tuning assembly, all housed on a single substrate or a single die. By implementing a resonator tuning assembly on the same substrate/die as the qubits and its resonator(s), the resonant frequency of the resonator can be controlled on-chip. In this manner, the resonant frequency can be fine-tuned to compensate for manufacturing variations or changed for any other purposes, as needed. Integration of means for varying the resonator frequency with the resonator and the qubits can greatly reduce complexity and lower the cost of quantum computing devices and provide an approach that can be efficiently used in large-scale manufacturing. Methods for fabricating such quantum devices are also disclosed. [0017] In some embodiments, the resonator tuning assembly described herein may be implemented as a wire or a line configured to carry current, the terms "wire" and "line" being used interchangeable hereafter. Such a wire is referred to herein as a "resonator tuning wire" because the resonant frequency of the resonator may be varied via a magnetic field generated as a result of the current flowing through the wire. As used herein, the term "wire" or "line" in context of resonator tuning wires does not necessarily imply a current carrying wire implemented in a straight line geometry. In fact, any geometry of such a wire may be used according to various embodiments of the present disclosure, such as e.g. a straight line or a shape comprising one or more curves or/and angles.

[0018] For the purposes of the present disclosure, the terms such as "upper," "lower," "over," "under," "between," and "on" as used herein refer to a relative position of one material layer or component with respect to other layers or components. For example, one layer disposed over or under another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer disposed between two layers may be directly in contact with the two layers or may have one or more intervening layers. In contrast, a first layer "on" a second layer is in direct contact with that second layer. Similarly, unless explicitly stated otherwise, one feature disposed between two features may be in direct contact with the adjacent features or may have one or more intervening layers.

[0019] The phrase "A and/or B" means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase "A, B, and/or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C). The term "between," when used with reference to measurement ranges, is inclusive of the ends of the measurement ranges. As used herein, the notation "A/B/C" means (A), (B), and/or (C).

[0020] The description uses the phrases "in an embodiment" or "in embodiments," which may each refer to one or more of the same or different embodiments. Furthermore, the terms "comprising," "including," "having," and the like, as used with respect to embodiments of the present disclosure, are synonymous. The disclosure may use perspective-based descriptions such as "above," "below," "top," "bottom," and "side"; such descriptions are used to facilitate the discussion and are not intended to restrict the application of disclosed embodiments. The accompanying drawings are not necessarily drawn to scale.

[0021] As used herein, terms indicating what may be considered an idealized behavior, such as e.g. "superconducting" or "lossless", are intended to cover functionality that may not be exactly ideal but is within acceptable margins for a given application. For example, a certain level of loss, either in terms of non-zero electrical resistance or non-zero amount of spurious two-level systems (TLS's) may be acceptable such that the resulting materials and structures may still be referred to by these "idealized" terms. Specific values associated with an acceptable level of loss are expected to change over time as fabrication precision will improve and as fault-tolerant schemes may become more tolerant of higher losses, all of which are within the scope of the present disclosure. [0022] Furthermore, while the present disclosure may include references to microwave signals, this is done only because current qubits are designed to work with such signals because the energy in the microwave range is higher than thermal excitations at the temperature that qubits are operated at. In addition, techniques for the control and measurement of microwaves are well known. For these reasons, typical frequencies of qubits are in 5-10 gigahertz (GHz) range, in order to be higher than thermal excitations, but low enough for ease of microwave engineering. However, advantageously, because excitation energy of qubits is controlled by the circuit elements, qubits can be designed to have any frequency. Therefore, in general, qubits could be designed to operate with signals in other ranges of electromagnetic spectrum and embodiments of the present disclosure could be modified accordingly. All of these alternative implementations are within the scope of the present disclosure.

[0023] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown, by way of illustration, embodiments that may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense.

[0024] Furthermore, in the following description, various aspects of the illustrative implementations will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that the present disclosure may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the illustrative implementations. However, it will be apparent to one skilled in the art that the present disclosure may be practiced without the specific details. In other instances, well- known features are omitted or simplified in order not to obscure the illustrative implementations.

[0025] Various operations will be described as multiple discrete operations, in turn, in a manner that is most helpful in understanding the present disclosure. However, the order of description should not be construed to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation. Operations described may be performed in a different order from the described embodiment(s). Various additional operations may be performed, and/or described operations may be omitted in additional embodiments.

Integrated frequency tuning of resonator structures

[0026] The ability to manipulate and read out quantum states, making quantum-mechanical phenomena visible and traceable, and the ability to deal with and improve on the fragility of quantum states of a qubit present unique challenges not found in classical computers. These challenges explain why so many current efforts of the industry and the academics continue to focus on a search for new and improved physical systems whose functionality could approach that expected of theoretically designed qubits. Physical systems for implementing qubits that have been explored until now include e.g. quantum dot devices, superconducting devices, single trapped ion devices, photon polarization devices, etc. To indicate that these devices implement qubits, sometimes these devices are referred to as qubits, e.g. quantum dot qubits, superconducting qubits, etc.

[0027] Integrated assemblies for providing on-chip resonant frequency control for resonator structures in quantum circuits described herein may be implemented with any type of qubits that rely on the use of resonators. Some exemplary circuit components are described below with reference to

superconducting qubits. However, integration of resonator tuning assemblies, e.g. implemented as current-carrying wires on the same die with the qubits and the resonator(s), as described herein, is applicable to quantum circuit components that include resonators coupled to any type of qubits, such as but not limited to quantum dot qubits, all of which are within the scope of the present disclosure.

[0028] FIG. 1 provides a schematic illustration of an example quantum circuit 100, according to some embodiments of the present disclosure. As shown in FIG. 1, an exemplary quantum circuit 100 includes a plurality of qubits 102. The qubits 102 may be implemented as any of the suitable qubits, such as e.g. superconducting qubits (e.g. transmons), quantum dot qubits, etc.

[0029] As also shown in FIG. 1, an exemplary quantum circuit 100 may further include at least one, but typically a plurality of, resonators 104, e.g. coupling and readout resonators.

[0030] Coupling resonators allow coupling different qubits together in order to realize quantum logic gates. A coupling resonator may be implemented as a microwave transmission line that includes capacitive connections to ground on both sides (i.e. a half wavelength resonator), which results in oscillations (resonance) within the transmission line. Each side of a coupling resonator is coupled, either capacitively or inductively, to a respective (i.e. different) qubit by being in sufficient proximity to the qubit. Because each side of a coupling resonator has coupling with a respective different qubit, the two qubits are coupled together through the coupling resonator. In this manner, state of one qubit depends on the state of the other qubit, and the other way around. Thus, coupling resonators may be employed in order to use a state of one qubit to control a state of another qubit, a necessary functionality for implementing logic gates.

[0031] Readout resonators may be used to read the state(s) of qubits. In some embodiments, a corresponding readout resonator may be provided for each qubit. A readout resonator is similar to a coupling resonator in that it may be implemented as a transmission line that includes a capacitive connection to ground on one side. On the other side, a readout resonator may either have a capacitive connection to ground (for a half wavelength resonator) or may be shorted to the ground (for a quarter wavelength resonator), which also results in oscillations within the transmission line, with the resonant frequency of the oscillations being close to the frequency of the qubit. A readout resonator is coupled to a qubit by being in sufficient proximity to the qubit, again, either through capacitive or inductive coupling. Due to a coupling between a readout resonator and a qubit, changes in the state of the qubit result in changes of the resonant frequency of the readout resonator. In turn, changes in the resonant frequency of the readout resonator can be read externally via e.g. wire bonding pads.

[0032] At least some of the resonators 104 shown in FIG. 1 may be implemented as resonant transmission lines, e.g. as resonant microwave transmission lines. To that end, any architecture suitable for microwave transmission may be used, such as e.g. coplanar waveguide, stripline, microstrip line, or inverted microstripline architectures.

[0033] Coupling resonators and readout resonators 104 may be considered as interconnects for supporting propagation of microwave signals in a quantum circuit. In addition to such resonant structures, a typical quantum circuit also includes non-resonant microwave transmission lines (not shown in FIG. 1) for providing microwave signals to different quantum circuit elements and

components, such as e.g. flux bias lines, microwave lines, or drive lines used with transmon qubits, which is one type of superconducting qubits. In general, the resonators 104 differ from non-resonant microwave transmission lines in that the resonators are configured for capacitive coupling to other circuit elements at one or both ends in order to have resonant oscillations, whereas non-resonant transmission lines may be similar to conventional microwave transmission lines because there is no resonance in these lines.

[0034] In various embodiments, the resonators 104 included in a quantum circuit could have different shapes and layouts. In general, the term "line" as used herein in context of the resonators 104 does not imply straight lines, unless specifically stated so. For example, some resonant transmission lines or parts thereof (e.g. conductor strips of transmission lines) may comprise more curves and turns while other resonant transmission lines or parts thereof may comprise less curves and turns, and some resonant transmission lines or parts thereof may comprise substantially straight lines.

[0035] In some embodiments, materials forming the resonators 104 may include aluminum (Al), niobium (Nb), niobium nitride (NbN), titanium nitride (TiN), molybdenum rhenium (MoRe), and niobium titanium nitride (NbTiN), all of which are particular types of superconductors. However, in various embodiments, other suitable superconductors, or alloys of different superconductors, may be used as well.

[0036] The qubits 102 and the resonators 104 of the quantum circuit 100 may be provided on, over, or at least partially embedded in a substrate (not shown in FIG. 1). The substrate may include any semiconductor material or materials suitable for realizing quantum circuit components thereon, in particular suitable for housing components of the quantum circuit 100. In one implementation, the substrate may be a crystalline substrate such as, but not limited to a silicon or a sapphire substrate, and may be provided as a wafer or a portion thereof. In other implementations, the substrate may be noncrystalline. In general, any material that provides sufficient advantages (e.g. sufficiently good electrical isolation and/or ability to apply known fabrication and processing techniques) to outweigh the possible disadvantages (e.g. negative effects of spurious two-level systems), and that may serve as a foundation upon which a quantum circuit may be built, falls within the spirit and scope of the present disclosure. Additional examples of substrates to be used for housing the quantum circuit 100 include silicon-on- insulator (SOI) substrates, lll-V substrates, and quartz substrates.

[0037] As further shown in FIG. 1, in addition to the qubits 102 and the resonators 104, the quantum circuit 100 further includes a resonator tuning assembly 106 configured to control resonant frequencies of the resonators 104, as described herein. The resonator tuning assembly 106 is provided, in an integrated manner, on the same substrate on which the qubits and the resonator 104 are disposed. For example, the qubits 102, the resonator(s) 104, and the resonator tuning assembly 106 may be provided on a single die, where, in general, the term "die" refers to a small block of semiconductor material on which a particular functional circuit is fabricated. An integrated circuit (IC) chip, also referred to as simply a chip or a microchip, sometimes refers to a semiconductor wafer on which thousands or millions of such devices or dies are fabricated. Other times, an IC chip refers to a portion of a semiconductor wafer (e.g. after the wafer has been diced) containing one or more dies. In general, a device is referred to as "integrated" if it is manufactured on one or more dies of an IC chip. By implementing the resonator tuning assembly 106 on the same die as the qubits 102 and the resonator(s) 104, the resonant frequencies of the resonators 104 may advantageously be controlled on- chip.

[0038] In various embodiments, quantum circuits such as the one shown in FIG. 1 may be used to implement components associated with a quantum IC. Such components may include those that are mounted on or embedded in a quantum IC, or those connected to a quantum IC. The quantum IC may be either analog or digital and may be used in a number of applications within or associated with quantum systems, such as e.g. quantum processors, quantum amplifiers, quantum sensors, etc., depending on the components associated with the integrated circuit. The integrated circuit may be employed as part of a chipset for executing one or more related functions in a quantum system.

[0039] FIG. 2 provides an illustration of an exemplary quantum computing device that may include any of the integrated assemblies for providing on-chip resonant frequency control for resonator structures in quantum circuits described herein, e.g. a quantum computer, 200, according to some embodiments of the present disclosure.

[0040] A number of components are illustrated in FIG. 2 as included in the quantum computing device 200, but any one or more of these components may be omitted or duplicated, as suitable for the application. In some embodiments, some or all of the components included in the quantum computing device 200 may be attached to one or more printed circuit boards (e.g., a motherboard). In some embodiments, various ones of these components may be fabricated onto a single system-on-a-chip (SoC) die. Additionally, in various embodiments, the quantum computing device 200 may not include one or more of the components illustrated in FIG. 2, but the quantum computing device 200 may include interface circuitry for coupling to the one or more components. For example, the quantum computing device 200 may not include a display device 206, but may include display device interface circuitry (e.g., a connector and driver circuitry) to which a display device 206 may be coupled. In another set of examples, the quantum computing device 200 may not include an audio input device 218 or an audio output device 208, but may include audio input or output device interface circuitry (e.g., connectors and supporting circuitry) to which an audio input device 218 or audio output device 208 may be coupled.

[0041] The quantum computing device 200 may include a processing device 202 (e.g., one or more processing devices). As used herein, the term "processing device" or "processor" may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory. The processing device 202 may include a quantum processing device 226 (e.g., one or more quantum processing devices), and a non-quantum processing device 228 (e.g., one or more non-quantum processing devices). The quantum processing device 226 may include one or more of the quantum circuits 100 disclosed herein, and may perform data processing by performing operations on the qubits 102 that may be generated in the quantum circuits 100, and monitoring the result of those operations. For example, as discussed above, different qubits may be allowed to interact, the quantum states of different qubits may be set or transformed, and the quantum states of qubits may be read (e.g., by another qubit via a coupling resonator or externally via a readout resonator). The quantum processing device 226 may be a universal quantum processor, or specialized quantum processor configured to run one or more particular quantum algorithms. In some embodiments, the quantum processing device 226 may execute algorithms that are particularly suitable for quantum computers, such as

cryptographic algorithms that utilize prime factorization, encryption/decryption, algorithms to optimize chemical reactions, algorithms to model protein folding, etc. The quantum processing device 226 may also include support circuitry to support the processing capability of the quantum processing device 226, such as input/output channels, multiplexers, signal mixers, quantum amplifiers, and analog-to- digital converters.

[0042] As noted above, the processing device 202 may include a non-quantum processing device 228. In some embodiments, the non-quantum processing device 228 may provide peripheral logic to support the operation of the quantum processing device 226. For example, the non-quantum processing device 228 may control the performance of a read operation, control the performance of a write operation, control the clearing of quantum bits, etc. The non-quantum processing device 228 may also perform conventional computing functions to supplement the computing functions provided by the quantum processing device 226. For example, the non-quantum processing device 228 may interface with one or more of the other components of the quantum computing device 200 (e.g., the communication chip 212 discussed below, the display device 206 discussed below, etc.) in a conventional manner, and may serve as an interface between the quantum processing device 226 and conventional components. The non-quantum processing device 228 may include one or more digital signal processors (DSPs), application-specific integrated circuits (ASICs), central processing units (CPUs), graphics processing units (GPUs), crypto processors (specialized processors that execute cryptographic algorithms within hardware), server processors, or any other suitable processing devices.

[0043] The quantum computing device 200 may include a memory 204, which may itself include one or more memory devices such as volatile memory (e.g., dynamic random access memory (DRAM)), nonvolatile memory (e.g., read-only memory (ROM)), flash memory, solid state memory, and/or a hard drive. In some embodiments, the states of qubits in the quantum processing device 226 may be read and stored in the memory 204. In some embodiments, the memory 204 may include memory that shares a die with the non-quantum processing device 228. This memory may be used as cache memory and may include embedded dynamic random access memory (eDRAM) or spin transfer torque magnetic random-access memory (STT-MRAM).

[0044] The quantum computing device 200 may include a cooling apparatus 224. The cooling apparatus 224 may maintain the quantum processing device 226 at a predetermined low temperature during operation to reduce the effects of scattering in the quantum processing device 226. This predetermined low temperature may vary depending on the setting; in some embodiments, the temperature may be 5 degrees Kelvin or less. In some embodiments, the non-quantum processing device 228 (and various other components of the quantum computing device 200) may not be cooled by the cooling apparatus 224, and may instead operate at room temperature. The cooling apparatus 224 may be, for example, a dilution refrigerator, a helium-3 refrigerator, or a liquid helium refrigerator.

[0045] In some embodiments, the quantum computing device 200 may include a communication chip 212 (e.g., one or more communication chips). For example, the communication chip 212 may be configured for managing wireless communications for the transfer of data to and from the quantum computing device 200. The term "wireless" and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a nonsolid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not.

[0046] The communication chip 212 may implement any of a number of wireless standards or protocols, including but not limited to Institute for Electrical and Electronic Engineers (IEEE) standards including Wi-Fi (IEEE 1402.11 family), IEEE 1402.16 standards (e.g., IEEE 1402.16-2005 Amendment), Long-Term Evolution (LTE) project along with any amendments, updates, and/or revisions (e.g., advanced LTE project, ultramobile broadband (UMB) project (also referred to as "3GPP2"), etc.). IEEE 1402.16 compatible Broadband Wireless Access (BWA) networks are generally referred to as WiMAX networks, an acronym that stands for Worldwide Interoperability for Microwave Access, which is a certification mark for products that pass conformity and interoperability tests for the IEEE 1402.16 standards. The communication chip 212 may operate in accordance with a Global System for Mobile Communication (GSM), General Packet Radio Service (GPRS), Universal Mobile Telecommunications System (UMTS), High Speed Packet Access (HSPA), Evolved HSPA (E-HSPA), or LTE network. The communication chip 212 may operate in accordance with Enhanced Data for GSM Evolution (EDGE), GSM EDGE Radio Access Network (GERAN), Universal Terrestrial Radio Access Network (UTRAN), or Evolved UTRAN (E-UTRAN). The communication chip 212 may operate in accordance with Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Digital Enhanced Cordless

Telecommunications (DECT), Evolution-Data Optimized (EV-DO), and derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The communication chip 212 may operate in accordance with other wireless protocols in other embodiments. The quantum computing device 200 may include an antenna 222 to facilitate wireless communications and/or to receive other wireless communications (such as AM or FM radio transmissions).

[0047] In some embodiments, the communication chip 212 may manage wired communications, such as electrical, optical, or any other suitable communication protocols (e.g., the Ethernet). As noted above, the communication chip 212 may include multiple communication chips. For instance, a first communication chip 212 may be dedicated to shorter-range wireless communications such as Wi-Fi or Bluetooth, and a second communication chip 212 may be dedicated to longer-range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, EV-DO, or others. In some

embodiments, a first communication chip 212 may be dedicated to wireless communications, and a second communication chip 212 may be dedicated to wired communications.

[0048] The quantum computing device 200 may include battery/power circuitry 214. The

battery/power circuitry 214 may include one or more energy storage devices (e.g., batteries or capacitors) and/or circuitry for coupling components of the quantum computing device 200 to an energy source separate from the quantum computing device 200 (e.g., AC line power).

[0049] The quantum computing device 200 may include a display device 206 (or corresponding interface circuitry, as discussed above). The display device 206 may include any visual indicators, such as a heads-up display, a computer monitor, a projector, a touchscreen display, a liquid crystal display (LCD), a light-emitting diode display, or a flat panel display, for example.

[0050] The quantum computing device 200 may include an audio output device 208 (or corresponding interface circuitry, as discussed above). The audio output device 208 may include any device that generates an audible indicator, such as speakers, headsets, or earbuds, for example.

[0051] The quantum computing device 200 may include an audio input device 218 (or corresponding interface circuitry, as discussed above). The audio input device 218 may include any device that generates a signal representative of a sound, such as microphones, microphone arrays, or digital instruments (e.g., instruments having a musical instrument digital interface (M IDI) output).

[0052] The quantum computing device 200 may include a global positioning system (GPS) device 216

(or corresponding interface circuitry, as discussed above). The GPS device 216 may be in communication with a satellite-based system and may receive a location of the quantum computing device 200, as known in the art.

[0053] The quantum computing device 200 may include an other output device 210 (or corresponding interface circuitry, as discussed above). Examples of the other output device 210 may include an audio codec, a video codec, a printer, a wired or wireless transmitter for providing information to other devices, or an additional storage device.

[0054] The quantum computing device 200 may include an other input device 220 (or corresponding interface circuitry, as discussed above). Examples of the other input device 220 may include an accelerometer, a gyroscope, a compass, an image capture device, a keyboard, a cursor control device such as a mouse, a stylus, a touchpad, a bar code reader, a Quick Response (QR) code reader, any sensor, or a radio frequency identification (RFID) reader.

[0055] The quantum computing device 200, or a subset of its components, may have any appropriate form factor, such as a hand-held or mobile computing device (e.g., a cell phone, a smart phone, a mobile internet device, a music player, a tablet computer, a laptop computer, a netbook computer, an ultrabook computer, a personal digital assistant (PDA), an ultramobile personal computer, etc.), a desktop computing device, a server or other networked computing component, a printer, a scanner, a monitor, a set-top box, an entertainment control unit, a vehicle control unit, a digital camera, a digital video recorder, or a wearable computing device.

[0056] In the following, for simplicity, control of resonant frequencies using the resonator tuning assembly 106 is explained with reference to controlling the resonant frequency of a single resonator. However, these explanations can easily be extended to individually controlling resonant frequencies of different resonators.

[0057] FIG. 3 provides a schematic illustration 300 of a magnetic field B generated by a current- carrying wire 302, according to some embodiments of the present disclosure. FIG. 3 illustrates current I flowing through the wire 302 in the direction as shown in FIG. 3 with an arrow within the wire 302. As a result of running the current through the wire 302, magnetic field B is created around the line.

Magnetic field B generated by the current-carrying wire 302 radially extends from the current-carrying wire 302 in the planes which are perpendicular to the line 302, shown in FIG. 3 with an exemplary plane 304 (direction of the magnetic field B shown with arrows in the plane 304). If the current-carrying wire 302 is provided in the plane of the drawing of FIG. 3, then the plane 304 is perpendicular to that plane and perpendicular to the line 302. If such a magnetic field is in sufficient proximity to a resonator, such as e.g. one of the resonators 104, e.g. by a portion of the current-carrying wire 302 being provided in the vicinity of the resonator 104, the magnetic field B may couple to the resonator 104, thereby changing the resonant frequency of the resonator 104. The strength of the magnetic field determines the shift in resonance frequency. Thus, a current-carrying wire such as the wire 302 provides means for controlling the resonant frequency of a resonator. Such a wire may, therefore, be referred to as a "resonator tuning wire" and may be used to implement the resonator tuning assembly 106 shown in FIG. 1. In various embodiments, the resonator tuning assembly 106 may include multiple resonator tuning wires 302 in order to enable supplying different currents to each of the wires to allow for independent tuning of resonant frequencies of different resonators. In addition, although the resonator tuning wire 302 is shown to have a circular cross-section and is shown as a straight line, in various embodiments such a wire may take on any other suitable shape, with the exact distribution of the magnetic field B being in accordance with electromagnetic principles.

[0058] In some embodiments, once the resonant frequency of a resonator has been tuned to a desired value by providing appropriate current to the wire 302 corresponding to the resonator, the resonator may be used to couple qubits or read a state of a qubit, depending on whether the resonator is a coupling resonator or a readout resonator.

[0059] For example, if a resonator for which the resonant frequency was tuned using the wire 302 is a coupling resonator, and if it is desirable that a first qubit and a second qubit of the plurality of qubits 102 interact via this coupling resonator connecting these qubits, then both qubits may need to be tuned to be at nearly the same frequency as the resonant frequency of the coupling resonator. One way in which such two qubits could interact is that, if the frequency of the first qubit is tuned very close to the resonant frequency of the coupling resonator, the first qubit can, when in the excited state, relax back down to the ground state by emitting a photon (similar to how an excited atom would relax) that would resonate within the coupling resonator. If the second qubit is also at this energy (i.e. if the frequency of the second qubit is also tuned very close to the resonant frequency of the coupling resonator), then it can absorb the photon emitted from the first qubit, via the coupling resonator, and be excited from it's ground state to an excited state. Thus, the two qubits "interact" in that a state of one qubit is controlled by the state of another qubit. In other scenarios, two qubits could interact via a coupling resonator at specific frequencies, but these three elements do not have to be tuned to be at nearly the same frequency with one another. In general, two or more qubits could be configured to interact with one another by tuning their frequencies to specific values or ranges with respect to the resonant frequency of the coupling resonator.

[0060] On the other hand, it may sometimes be desirable that two qubits coupled by a coupling resonator do not interact, i.e. the qubits are independent (sometimes referred to as "de-tuned"). In this case, it is possible to cause the frequency of one qubit to change enough, e.g. by applying magnetic flux to the qubit, so that the photon it could emit no longer has the right frequency to resonate on the coupling resonator. If there is nowhere for such a frequency-detuned photon to go, the qubit will be better isolated from its surroundings and will live longer in its current state. Thus, in general, two or more qubits could be configured to avoid or eliminate interactions with one another by tuning their frequencies to specific values or ranges with respect to the resonant frequency of the coupling resonator. [0061] In other embodiments, it can be assumed that the two qubits emit photons with almost identical frequencies (e.g. the difference in emission frequency may be 1 megaHertz (M Hz) or less for superconducting qubits) and, instead of tuning the frequencies of the qubits to allow them to interact or prevent them from interaction as described above, the frequency of the coupling resonator may be tuned, using the resonator tuning assembly as described herein. By providing appropriate current in the resonator tuning wire 302 corresponding to the coupling resonator, the resonant frequency of the coupling resonator may either be brought close to that of the qubits (in order to allow the qubits to be coupled) or be brought away from the frequency of the qubits (in order to prevent interaction of these two qubits via the coupling resonator). In some embodiments, when a resonant frequency of a coupling resonator differs from the resonant frequencies of qubits by less than a few hundred M Hz, the qubits would be able to interact via such a resonator, while having a resonant frequency of the coupling resonator deviating by a larger amount from that of the qubits would prevent qubits from interaction.

[0062] In another example, if a resonator for which the resonant frequency was tuned using the wire 302 is a readout resonator, the state(s) of each qubit 102 may be read by way of its corresponding readout resonator. To that end, a readout resonator may be provided for each qubit 102. The readout resonator is coupled to the qubit by being in sufficient proximity to the qubit, e.g. either through capacitive or inductive coupling. Due to a coupling between the readout resonator and the qubit, changes in the state of the qubit result in changes of the resonant frequency of the readout resonator. In turn, changes in the resonant frequency of the readout resonator induce changes in the current in a microwave line coupled to the readout resonator, and that current can be read externally, e.g. via the wire-bonding pads provided for the quantum circuit.

[0063] FIG. 4 provides a top-view schematic illustration of a portion 400 of a quantum device where control of the resonant frequency of a resonator 401 is implemented by providing a resonator tuning wire 402 in the same plane as the resonator, according to some embodiments of the present disclosure. The portion 400 of the quantum device could be one example of the quantum circuit 100 described herein, where the resonator 401 is one of the resonators 104 and the resonator tuning wire 402 is a part of the resonator tuning assembly 106. The qubits 102 are not shown in FIG. 4 in order to not clutter the drawing with details which would be different depending on the type of the qubits used and on whether the resonator 402 is a coupling or a readout resonator.

[0064] When current I, shown in FIG. 4 with an arrow 403, is provided within the resonator tuning wire 402, it generates the magnetic field B, as shown in FIG. 3, radially extending from the resonator tuning wire 402. Control of the resonant frequency of the resonator 401 may then be carried out using the resonator tuning wire 402 in a manner analogous to that described above with reference to the resonator tuning wire 302 shown in FIG. 3. Therefore, in the interests of brevity, this description is not repeated here. [0065] One advantage for providing the resonator tuning assembly in the same plane as the resonator(s) could be that the resonator(s) and the resonator tuning wire(s) of the resonator tuning assembly could be fabricating with at least some of the fabrication steps overlapping in time or being performed one right after the other. For example, superconducting materials for forming both the resonator(s) and the resonator tuning wire(s) could be deposited at the same time, e.g. using sputter. After that, the resonator(s) and the resonator tuning wire(s) could be patterned and etched, using masks appropriate for each. In another example, both the resonator(s) and the resonator tuning wire(s) could be fabricated at the same time using substrate doping, followed by activation of implanted dopants.

[0066] At least portions of qubits 102 could also be formed using some fabrication steps overlapping with those used to form in-plane resonator tuning assembly 106. For example, for quantum dot qubits, the resonator(s) and the resonator tuning wire(s) could be formed at the same time, or overlapping, with the fabrication of the gates used to initialize and manipulate quantum dots. In such embodiments, the same superconducting material could be used for the gates, the resonator(s) and the resonator tuning wire(s), with appropriate patterning and etching of each, as desired.

[0067] FIG. 4 provides one illustration of how the resonator tuning wire 402 could be arranged with respect to the resonator 401 that the wire is supposed to tune. As shown in FIG. 4, the shape of the resonator tuning wire 402 may conform (i.e. follow, within a predefined deviation) to the shape of the resonator 401. In various embodiments, geometries of other resonator tuning wires in-plane with the corresponding resonator may be different from that illustrated in FIG. 4. A specific geometry for a resonator tuning wire may be selected based on considerations such as e.g. the size and the location of the resonator, the amount of magnetic field to be generated by the resonator tuning wire, and ease of fabrication. In order for the magnetic field generated by the resonator tuning wire 402 to adequately tune the resonant frequency of the resonator 401, the resonator tuning wire 402 may be implemented so that, at each point along at least a portion of the resonator tuning wire 402, the distance (i.e. the shortest distance) between the wire 402 and the resonator 401 is below a predefined threshold (e.g. below 100 micrometers), or within a predefined range (e.g. between 50 nanometers and 100 micrometers).

[0068] FIG. 5 provides a top-view schematic illustration of a portion 500 of a quantum device where control of the resonant frequency of a resonator 501 is implemented by providing a resonator tuning wire 502 in a plane that is below the plane of the resonator, according to some embodiments of the present disclosure. The portion 500 of the quantum device could be one example of the quantum circuit 100 described herein, where the resonator 501 is one of the resonators 104 and the resonator tuning wire 502 is a part of the resonator tuning assembly 106. The qubits 102 are not shown in FIG. 5 in order to not clutter the drawing with details which would be different depending on the type of the qubits used and on whether the resonator 502 is a coupling or a readout resonator. [0069] When current I, shown in FIG. 5 with an arrow 503, is provided within the resonator tuning wire 502, it generates the magnetic field B, as shown in FIG. 3, radially extending from the resonator tuning wire 502. Control of the resonant frequency of the resonator 501 may then be carried out using the resonator tuning wire 502 in a manner analogous to that described above with reference to the resonator tuning wire 302 shown in FIG. 3. Therefore, in the interests of brevity, this description is not repeated here.

[0070] One advantage for providing the resonator tuning assembly below the plane of the resonator(s) could be to preserve space in the plane of the resonators for providing more active components such as the qubits and the resonators.

[0071] FIG. 5 provides one illustration of how the resonator tuning wire 502 could be arranged with respect to the resonator 501 that the wire is supposed to tune. As shown in FIG. 5, the shape of the resonator tuning wire 502 may conform to the shape of the resonator 501. In some embodiments, the shape of the resonator tuning wire 502 may be such that, if the resonator tuning wire 502 and the resonator 501 are projected onto a single plane parallel to the surface of the substrate, a projection of the resonator tuning wire 502 and a projection of the resonator 501 would substantially overlap (i.e. the resonator tuning wire 502 is provided immediately below and follows the shape of the resonator 501).

[0072] In various embodiments, geometries of other resonator tuning wires below the plane of the corresponding resonator may be different from that illustrated in FIG. 5. A specific geometry for a resonator tuning wire may be selected based on considerations such as e.g. the size and the location of the resonator, the amount of magnetic field to be generated by the resonator tuning wire, and ease of fabrication. In order for the magnetic field generated by the resonator tuning wire 502 to adequately tune the resonant frequency of the resonator 501, the resonator tuning wire 502 may be implemented so that, at each point along at least a portion of the resonator tuning wire 502, the distance (i.e. the shortest distance) between the wire 502 and the resonator 501 is below a predefined threshold (e.g. below 100 micrometers), or within a predefined range (e.g. between 50 nanometers and 100 micrometers).

[0073] In still further embodiments, a resonator tuning wire may be provided above the plane of the resonator which resonant frequency the wire is supposed to tune. Descriptions provided above for the below-plane resonator tuning wire 502 can be extended for resonator tuning wires provided above the plane of the resonator. Therefore, in the interests of brevity, these descriptions are not repeated here.

[0074] In various embodiments, any suitable techniques may be used to manufacture quantum devices including quantum circuits 100 disclosed herein. FIG. 6 is a flow diagram of an illustrative method 1000 of manufacturing a quantum device, according to some embodiments of the present disclosure. Although the operations discussed below with reference to the method 1000 are illustrated in a particular order and depicted once each, these operations may be repeated or performed in a different order (e.g., in parallel), as suitable. Additionally, various operations may be omitted, as suitable. Various operations of the method 1000 may be illustrated with reference to one or more of the embodiments discussed above, but the method 1000 may be used to manufacture any suitable quantum device (including any suitable ones of the embodiments disclosed herein).

[0075] At 1002, qubits 102 and resonator(s) 104 could be provided on a substrate and, at 1004, the resonator tuning assembly 106 could be provided on the same substrate. The order of 1002 and 1004 would depend on whether the resonator tuning assembly 106 is provided below, above, or in plane with the resonator(s) 104 the resonant frequency/frequencies of which the resonator tuning assembly 106 is intended to tune, as described above.

[0076] At 1006, the resonator tuning assembly 106 is provided with means for connecting the assembly to a current source so that, during operation of the quantum device, current can be provided in the resonator tuning wire(s) of the assembly 106 in order to tune one or more resonant frequencies of the resonators 104.

[0077] FIGs. 7-8 are flow diagrams of different illustrative methods 1010 and 1020, respectively, of operating a quantum device, according to some embodiments of the present disclosure. Although the operations discussed below with reference to each of the methods 1010 and 1020 are illustrated in a particular order and depicted once each, these operations may be repeated or performed in a different order (e.g., in parallel), as suitable. Additionally, various operations may be omitted, as suitable.

Various operations of each of the methods 1010 and 1020 may be illustrated with reference to one or more of the embodiments discussed above, but each of the methods 1010 and 1020 may be used to operate any suitable quantum device (including any suitable ones of the embodiments disclosed herein).

[0078] Turning to the method 1010 of FIG. 7, at 1012, current is supplied to the resonator tuning assembly 106. The example of the method illustrated in FIG. 7 is provided for the resonator being a coupling resonator. As previously described herein, when current is supplied to the one or more wires of the resonator tuning assembly 106, respective magnetic fields are generated around each of the wires, radially extending from the wires and tuning the resonant frequency of the associated coupling resonators. Once the resonant frequency of the coupling resonator has been tuned, then, at 1014, the resonator may be used to couple two or more qubits together or decouple these qubits, as described above. In case when a resonant frequency of a coupling resonator is varied in order to couple or decouple qubits (i.e. in the case when resonant frequencies of the two or more qubits coupled by the coupling resonator are the same), then tuning the resonant frequency of the coupling resonator, at 1012, to the same resonant frequency as that of the qubits would ensure that, at 1014, the qubits can interact via the coupling resonator. On the other hand, tuning the resonant frequency of the coupling resonator, at 1012, to a resonant frequency that is away from that of the qubits would ensure that, at 1014, the qubits are de-tuned, i.e. cannot interact with one another via the coupling resonator. [0079] Turning to the method 1020 of FIG. 8, at 1022, current is supplied to the resonator tuning assembly 106. The example of the method illustrated in FIG. 7 is provided for the resonator being a readout resonator. Again, when current is supplied to the one or more wires of the resonator tuning assembly 106, respective magnetic fields are generated around each of the wires, radially extending from the wires and tuning the resonant frequency of the associated readout resonators. Once the resonant frequency of the readout resonator has been tuned, at 1014, the resonator is used to sense a state of a corresponding qubit, as described above. In some embodiments, prior to sensing the state of a qubit at 1024, the qubit may be allowed to interact with one or more other qubits, e.g. using the coupling resonator as described with reference to he method 1010 of FIG. 7.

Selected Examples

[0080] Some Examples in accordance with various embodiments of the present disclosure are now described.

[0081] Example 1 provides a quantum device, including a substrate housing a plurality of qubits and at least one resonator, and a resonator tuning assembly provided on or in the substrate, the resonator tuning assembly configured to control a resonant frequency of the at least one resonator.

[0082] Example 2 provides the quantum device according to Example 1, where the resonator tuning assembly includes an electrically conductive wire (i.e. a wire configured to carry current).

[0083] Example 3 provides the quantum device according to Example 2, where the wire is disposed in a single plane as the at least one resonator.

[0084] Example 4 provides the quantum device according to Example 2, where the wire is disposed in a plane different from that in which the at least one resonator is disposed (i.e. the resonator tuning wire may be provided out-of-plane with the resonator, e.g. below the resonator plane or above the resonator plane).

[0085] Example 5 provides the quantum device according to any one of Examples 2-4, where, for each point of at least a portion of the wire, a shortest distance between the wire and the at least one resonator is between 50 nanometers and 100 micrometers.

[0086] Example 6 provides the quantum device according to any one of Examples 2-5, where a shape of at least a portion of the wire conforms to a shape of at least a portion of the at least one resonator.

[0087] Example 7 provides the quantum device according to any one of Examples 2-6, where the wire includes a material of the substrate doped to be electrically conductive.

[0088] Example 8 provides the quantum device according to any one of Examples 2-6, where the wire includes a material of the substrate doped to be superconductive.

[0089] Example 9 provides the quantum device according to any one of Examples 2-6, where the wire includes one or more of superconductive materials. [0090] Example 10 provides the quantum device according to Example 9, where the one or more of superconductive materials includes one or more of aluminium (Al), niobium (Nb), niobium nitride (NbN), titanium nitride (TiN), molybdenum rhenium (Mo e), and niobium titanium nitride (NbTiN).

[0091] Example 11 provides the quantum device according to any one of the preceding Examples, where the at least one resonator includes a microwave transmission line configured to support resonant oscillations.

[0092] Example 12 provides the quantum device according to any one of the preceding Examples, where the at least one resonator is a coupling resonator configured to couple two or more of the plurality of qubits.

[0093] Example 13 provides the quantum device according to any one of Examples 1-11, where the at least one resonator is a readout resonator configured to read a quantum state of one or more of the plurality of qubits.

[0094] Example 14 provides the quantum device according to any one of Examples 1-13, where the plurality of qubits includes superconducting qubits.

[0095] Example 15 provides the quantum device according to any one of Examples 1-13, where the plurality of qubits includes quantum dot qubits.

[0096] Example 16 provides a method for fabricating a quantum device. The method includes providing a plurality of qubits on a substrate; providing at least one resonator on the substrate; and providing a resonator tuning assembly at least partially in or on the substrate, the resonator tuning assembly configured to control a resonant frequency of the at least one resonator.

[0097] Example 17 provides the method according to Example 16, where the resonator tuning assembly is provided on the substrate in a single plane with the at least one resonator, and providing the at least one resonator and the resonator tuning assembly on the substrate includes depositing superconductive material for forming the at least one resonator and the resonator tuning assembly, and patterning the deposited superconductive material to define shapes of the at least one resonator and the resonator tuning assembly.

[0098] Example 18 provides the method according to Example 17, where the superconducting material for forming the at least one resonator is deposited in a single step with a deposition of the

superconductive material for forming the resonator tuning assembly.

[0099] Example 19 provides the method according to Example 17, where the superconducting material is patterned to define a shape of the at least one resonator in a single step with patterning of the superconductive material to define a shape of the resonator tuning assembly.

[00100] Example 20 provides the method according to Example 16, where the resonator tuning assembly is provided on the substrate in a single plane with the at least one resonator, and providing the at least one resonator and the resonator tuning assembly on the substrate includes doping the substrate to be superconductive to define shapes of the at least one resonator and the resonator tuning assembly.

[00101] Example 21 provides the method according to Example 16, where the resonator tuning assembly is provided in a plane different from a plane in which the at least one resonator is provided, and where the method further includes providing a layer of dielectric material between the plane of the at least one resonator and the plane of the resonator tuning assembly.

[00102] Example 22 provides a method of operating a quantum device. The method includes supplying current to a resonator tuning assembly provided on or in a substrate to tune a resonant frequency of at least one readout resonator provided on the substrate, and sensing a quantum state of the a first qubit provided on the substrate with the readout resonator.

[00103] Example 23 provides the method according to Example 22, further including allowing the first qubit to interact with a second qubit provided on the substrate prior to sensing the quantum state of the first qubit.

[00104] In another Example, the method according to Example 22 further includes maintaining the substrate at a temperature below 5 degrees Kelvin during the operation of the quantum device.

[00105] Example 24 provides a method of operating a quantum device. The method includes supplying current to a resonator tuning assembly provided on or in a substrate to tune a resonant frequency of at least one coupling resonator provided on the substrate, and coupling a first qubit provided on the substrate to a second qubit provided on the substrate with the coupling resonator.

[00106] Example 25 provides the method according to Example 24, where the resonator tuning assembly is a first resonator tuning assembly and the method further includes supplying current to a second resonator tuning assembly provided on or in the substrate to tune a resonant frequency of at least one readout resonator provided on the substrate, and sensing a quantum state of the second qubit with the readout resonator.

[00107] In another Example, the method according to Examples 24 or 25 further includes maintaining the substrate at a temperature below 5 degrees Kelvin during the operation of the quantum device.

[00108]The above description of illustrated implementations of the disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. While specific implementations of, and examples for, the disclosure are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the disclosure, as those skilled in the relevant art will recognize.

[00109]These modifications may be made to the disclosure in light of the above detailed description. The terms used in the following claims should not be construed to limit the disclosure to the specific implementations disclosed in the specification and the claims. Rather, the scope of the disclosure is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.

Claims

1. A quantum device, comprising:

a substrate housing a plurality of qubits and at least one resonator; and

a resonator tuning assembly provided on or in the substrate, the resonator tuning assembly configured to control a resonant frequency of the at least one resonator.

2. The quantum device according to claim 1, wherein the resonator tuning assembly comprises an electrically conductive wire.

3. The quantum device according to claim 2, wherein the wire is disposed in a same plane as the at least one resonator.

4. The quantum device according to claim 2, wherein the wire is disposed in a plane different from that in which the at least one resonator is disposed.

5. The quantum device according to any one of claims 2-4, wherein, for each point of at least a portion of the wire, a shortest distance between the wire and the at least one resonator is between 50 nanometers and 100 micrometers.

6. The quantum device according to any one of claims 2-4, wherein a shape of at least a portion of the wire conforms to a shape of at least a portion of the at least one resonator.

7. The quantum device according to any one of claims 2-4, wherein the wire comprises a material of the substrate doped to be electrically conductive.

8. The quantum device according to any one of claims 2-4, wherein the wire comprises a material of the substrate doped to be superconductive.

9. The quantum device according to any one of claims 2-4, wherein the wire comprises one or more of superconductive materials.

10. The quantum device according to claim 9, wherein the one or more of superconductive materials comprises one or more of aluminium (Al), niobium (Nb), niobium nitride (NbN), titanium nitride (TiN), molybdenum rhenium (Mo e), and niobium titanium nitride (NbTiN).

11. The quantum device according to any one of claims 1-4, wherein the at least one resonator comprises a microwave transmission line configured to support resonant oscillations.

12. The quantum device according to any one of claims 1-4, wherein the at least one resonator is a coupling resonator configured to couple two or more of the plurality of qubits.

13. The quantum device according to any one of claims 1-4, wherein the at least one resonator is a readout resonator configured to read a quantum state of one or more of the plurality of qubits.

14. The quantum device according to any one of claims 1-4, wherein the plurality of qubits comprises superconducting qubits.

15. The quantum device according to any one of claims 1-4, wherein the plurality of qubits comprises quantum dot qubits.

16. A method for fabricating a quantum device, the method comprising: providing a plurality of qubits on a substrate;

providing at least one resonator on the substrate; and

providing a resonator tuning assembly at least partially in or on the substrate, the resonator tuning assembly configured to control a resonant frequency of the at least one resonator.

17. The method according to claim 16, wherein the resonator tuning assembly is provided on the substrate in a single plane with the at least one resonator, and providing the at least one resonator and the resonator tuning assembly on the substrate comprises:

depositing superconductive material for forming the at least one resonator and the resonator tuning assembly, and

patterning the deposited superconductive material to define shapes of the at least one resonator and the resonator tuning assembly.

18. The method according to claim 17, wherein the superconducting material for forming the at least one resonator is deposited in a shared step with a deposition of the superconductive material for forming the resonator tuning assembly.

19. The method according to claim 17, wherein the superconducting material is patterned to define a shape of the at least one resonator in a shared step with patterning of the superconductive material to define a shape of the resonator tuning assembly.

20. The method according to claim 16, wherein the resonator tuning assembly is provided on the substrate in a single plane with the at least one resonator, and providing the at least one resonator and the resonator tuning assembly on the substrate comprises doping the substrate to be superconductive to define shapes of the at least one resonator and the resonator tuning assembly.

21. The method according to claim 16, wherein the resonator tuning assembly is provided in a plane different from a plane in which the at least one resonator is provided, and wherein the method further comprises providing a layer of dielectric material between the plane of the at least one resonator and the plane of the resonator tuning assembly.

22. A method of operating a quantum device, the method comprising:

supplying current to a resonator tuning assembly provided on or in a substrate to tune a resonant frequency of at least one readout resonator provided on the substrate; and

sensing a quantum state of the a first qubit provided on the substrate with the readout resonator.

23. The method according to claim 22, further comprising allowing the first qubit to interact with a second qubit provided on the substrate prior to sensing the quantum state of the first qubit.

24. A method of operating a quantum device, the method comprising: supplying current to a resonator tuning assembly provided on or in a substrate to tune a resonant frequency of at least one coupling resonator provided on the substrate; and

coupling a first qubit provided on the substrate to a second qubit provided on the substrate with the coupling resonator.

25. The method according to claim 24, wherein the resonator tuning assembly is a first resonator tuning assembly, the method further comprising:

supplying current to a second resonator tuning assembly provided on or in the substrate to tune a resonant frequency of at least one readout resonator provided on the substrate; and

sensing a quantum state of the second qubit with the readout resonator.