EP-4736322-A1 - MULTIPOLE BANDPASS FILTER NETWORK BASED ISOLATOR DEVICES

Abstract

A device comprises filter circuitry and non-linear mixing devices. The filter circuitry comprises a first port, a second port, a first bandpass filter, and a second bandpass filter. The non-linear mixing devices are responsive to control signals to couple poles of the first bandpass filter to respective poles of the second bandpass filter to cause non-reciprocal transmission of signals from the first port to the second port.

Inventors

• BECK, MATTHEW
• SELVANAYAGAM, MICHAEL
• MANCINI, CORRADO

Assignees

• International Business Machines Corporation

Dates

Publication Date

20260506

Application Date

20240625

Claims (20)

1. 1. A device, comprising: filter circuitry comprising a first port, a second port, a first bandpass filter, and a second bandpass filter; and non-linear mixing devices which are responsive to control signals to couple poles of the first bandpass filter to respective poles of the second bandpass filter to cause non-reciprocal transmission of signals from the first port to the second port.
2. 2. The device of claim 1, wherein the first bandpass filter and the second bandpass filter each comprise an immittance inverting bandpass filter.
3. 3. The device of any of the preceding claims, wherein the non-linear mixing devices are driven by respective control signals having a same frequency and different phases.
4. 4. The device of claim 3, wherein the respective control signals have similar or different amplitudes.
5. 5. The device of any of the preceding claims, wherein: the first bandpass filter comprises a first passband with a first center frequency; the second bandpass filter comprises a second passband with a second center frequency; the first passband and the second passband are non-overlapping passbands; and the control signals are applied to the non-linear mixing devices and comprise radio frequency signals having a frequency which is a function of a difference between the first center frequency and the second center frequency.
6. 6. The device of any of the preceding claims, wherein the non-linear mixing devices comprise direct current superconducting quantum interference devices.
7. 7. The device of any of the preceding claims, wherein the non-linear mixing devices comprise Josephson parametric converter devices, wherein each Josephson parametric converter device comprises a Josephson ring modulator which is configured to couple respective poles of the first bandpass filter and the second bandpass filter.
8. 8. The device of any of the preceding claims, wherein: the first bandpass filter comprises a first terminal that is connected to the first port and a second terminal that is connected to the second port; the second bandpass filter comprises a first terminal that is terminated and a second terminal that is terminated.
9. 9. A system, comprising: a quantum processor comprising quantum bits; a readout signal path configured to transmit signals that are readout from one or more of the quantum bits of the quantum processor, the readout signal path comprising an isolator circuit which comprises: filter circuitry comprising a first port, a second port, a first bandpass filter, and a second bandpass filter; and non-linear mixing devices which are responsive to control signals to couple poles of the first bandpass filter to respective poles of the second bandpass filter to cause nonreciprocal transmission of signals through the isolator circuit from the first port to the second port.
10. 10. The system of claim 9, wherein the first bandpass filter and the second bandpass filter of the isolator circuit each comprise an immittance inverting bandpass filter.
11. 11. The system of any of claims 9 to 10, wherein the non-linear mixing devices of the isolator circuit are driven by respective control signals having a same frequency and different phases.
12. 12. The system of claim 11, wherein the respective control signals have similar or different amplitudes.
13. 13. The system of any of claims 9 to 12, wherein: the first bandpass filter comprises a first passband with a first center frequency; the second bandpass filter comprises a second passband with a second center frequency; the first passband and the second passband are non-overlapping passbands; and the control signals are applied to the non-linear mixing devices and comprise radio frequency signals having a frequency which is a function of a difference between the first center frequency and the second center frequency.
14. 14. The system of any of claims 9 to 13, wherein the non-linear mixing devices comprise direct current superconducting quantum interference devices.
15. 15. The system of any of claims 9 to 14, wherein the non-linear mixing devices comprise Josephson parametric converter devices, wherein each Josephson parametric converter device comprises a Josephson ring modulator which is configured to couple respective poles of the first bandpass filter and the second bandpass filter.
16. 16. The system of any of claims 9 to 15, wherein: the first bandpass filter comprises a first terminal that is connected to the first port and a second terminal that is connected to the second port; the second bandpass filter comprises a first terminal that is terminated and a second terminal that is terminated.
17. 17. A device, comprising: an isolator circuit, wherein the isolator circuit comprises: a first port and a second port; a first multipole immittance inverting bandpass filter; a second multipole immittance inverting bandpass filter; non-linear mixing devices which couple poles of the first multipole immittance inverting bandpass filter to respective poles of the second multipole immittance inverting bandpass filter; and a transmission line commonly coupled to each of the non-linear mixing devices, and configured to apply a control signal to each of the non-linear mixing devices at a given frequency with different phase shifts, to cause non-reciprocal transmission of signals from the first port to the second port of the isolator circuit.
18. 18. The device of claim 17, wherein: the first multipole immittance inverting bandpass filter comprises a first passband with a first center frequency; the second multipole immittance inverting bandpass filter comprises a second passband with a second center frequency; the first passband and the second passband are non-overlapping passbands; and the given frequency of the control signal is a function of a difference between the first center frequency and the second center frequency.
19. 19. A system, comprising: a quantum processor comprising quantum bits; a readout signal path configured to transmit signals that are readout from one or more of the quantum bits of the quantum processor, the readout signal path comprising an isolator circuit which comprises: a first port and a second port; a first multipole immittance inverting bandpass filter; a second multipole immittance inverting bandpass filter; non-linear mixing devices which couple poles of the first multipole immittance inverting bandpass filter to respective poles of the second multipole immittance inverting bandpass filter; and a transmission line commonly coupled to each of the non-linear mixing devices, and configured to apply a control signal to each of the non-linear mixing devices at a given frequency with different phase shifts, to cause non-reciprocal transmission of signals from the first port to the second port of the isolator circuit.
20. 20. The system of claim 19, wherein: the first multipole immittance inverting bandpass filter comprises a first passband with a first center frequency; the second multipole immittance inverting bandpass filter comprises a second passband with a second center frequency; the first passband and the second passband are non-overlapping passbands; and the given frequency of the control signal is a function of a difference between the first center frequency and the second center frequency.

Description

MULTIPOLE BANDPASS FILTER NETWORK BASED ISOLATOR DEVICES BACKGROUND [0001] This disclosure relates generally to quantum computing and, in particular, microwave isolator devices and isolation techniques for use with, e.g., superconducting quantum computing systems. A superconducting quantum computing system is implemented using circuit quantum electrodynamics (QED) devices, which utilize the quantum dynamics of electromagnetic fields in superconducting circuits that include superconducting quantum bits, to generate and process quantum information. In general, superconducting quantum bits (qubits) are electronic circuits which are implemented using components such as superconducting tunnel junctions (e.g., Josephson junctions), inductors, and/or capacitors, etc., and which behave as quantum mechanical anharmonic (non-linear) oscillators with quantized states, when cooled to cryogenic temperatures. [0002] The cryogenic hardware that is utilized to construct a quantum computer with superconducting qubits requires a variety of microwave components including microwave couplers, filter, amplifiers, circulators, and isolators. Traditionally, these components are implemented via discrete components that are implemented in qubit control and readout signal paths. As the number of qubits that are implemented in a quantum processor increases to hundreds or thousands or more, the integration of these peripheral components in a manner that reduces overall footprint, thermal load, and added noise in the overall system, is a key challenge to scaling. Ferrite-based microwave isolators are one of the physically largest devices that continue to remain as discrete components. They are generally employed in a qubit readout chain to protect qubits and resonators from broadband noise and unwanted signals emanating from downstream components such as amplifiers. As a consequence of their bulky construction, the need to place a large number of such ferrite-based microwave isolators at the mixing chamber of a dilution refrigerator to support increasing qubit counts poses a limitation to system scaling and integration. SUMMARY [0003] Exemplary embodiments of the disclosure include techniques for implementing isolation circuits that provide non-reciprocal transmission of signals in signal paths of a quantum computing system. For example, an exemplary embodiment includes a device which comprises filter circuitry and non-linear mixing devices. The filter circuitry comprises a first port, a second port, a first bandpass filter, and a second bandpass filter. The non-linear mixing devices are responsive to control signals to couple poles of the first bandpass filter to respective poles of the second bandpass filter to cause non-reciprocal transmission of signals from the first port to the second port. [0004] Advantageously, the device can be utilized in place of discrete ferrite-based isolator devices to enable non-reciprocal transmission of signals in the signal paths, e.g., qubit control and readout chains of a quantum computing system, and thereby reduce the cost and footprint for implementing isolation in such control and readout chains. The device provides a non-magnetic solution to isolation and can be disposed in relatively close proximity to a quantum processor and/or integrated therewith on an integrated circuit chip, while having a much smaller footprint as compared to discrete ferrite-based isolation devices, and while providing isolation and electrical characteristics that are similar to ferrite-based isolation devices. [0005] In another exemplary embodiment, a system comprises a quantum processor comprising quantum bits, and a readout signal path configured to transmit signals that are readout from one or more of the quantum bits of the quantum processor. The readout signal path comprises an isolator circuit. The isolator circuit comprises a first port, a second port, a first bandpass filter, and a second bandpass filter, and non-linear mixing devices. The nonlinear mixing devices are responsive to control signals to couple poles of the first bandpass filter to respective poles of the second bandpass filter to cause non-reciprocal transmission of signals through the isolator circuit from the first port to the second port. [0006] In another exemplary embodiment, as may be combined with the preceding paragraphs, the first bandpass filter comprises a first passband with a first center frequency and the second bandpass filter comprises a second passband with a second center frequency. The first passband and the second passband are non-overlapping passbands. The control signals applied to the non-linear mixing devices comprise radio frequency signals having a frequency which is a function of a difference between the first center frequency and the second center frequency. [0007] Advantageously, the isolator circuit with a multi -bandpass filter architecture allows the bandpass filters to be designed with disparate, non-overlapping p