Quantum computer hardware with reflectionless filters for thermalizing radio frequency signals

Patent metadata

Field	Value
Publication number	US-2020175412-A1
Application number	US-201916686761-A
Country	US
Kind code	A1
Filing date	Nov 18, 2019
Priority date	Dec 3, 2018
Publication date	Jun 4, 2020
Grant date	—

Abstract

A quantum computer hardware apparatus may include a first stage, which is connected to one or more signal generators, and a second stage adapted to be cooled down at a lower temperature than the first stage. Superconducting qubits are arranged in the second stage. The signal generators are configured, each, to generate radio frequency (RF) signals to drive the qubits, in operation. The apparatus may further include an intermediate stage between the first stage and the second stage, wherein the intermediate stage comprises one or more coolable filters, the latter configured for thermalizing RF signals from the signal generators. Related methods for thermalizing radio frequency signals in a quantum computer hardware apparatus are also disclosed.

First claim

What is claimed is:

1 . A quantum computer hardware apparatus, comprising:
a first stage connected to a signal generator; a second stage with superconducting qubits arranged therein, the second stage adapted to be cooled down at a lower temperature than the first stage, wherein the signal generator is configured to generate radio frequency signals to drive the qubits; and an intermediate stage between the first stage and the second stage, wherein the intermediate stage comprises at least a coolable filter, the coolable filter configured for thermalizing radio frequency signals from the signal generator, wherein said intermediate stage comprises CMOS-fabricated components, the CMOS-fabricated components including said coolable filter.

2 . The quantum computer hardware apparatus according to claim 1 , wherein
the first stage is adapted to be cooled at a temperature between 2 and 6 Kelvin, in operation of the apparatus.

3 . The quantum computer hardware apparatus according to claim 1 , wherein
the coolable filter is configured as a reflectionless bandpass filter, allowing a signal inside a passband thereof while absorbing signal in a stopband thereof.

4 . The quantum computer hardware apparatus according to claim 3 , wherein
the coolable filter is configured so as to have dynamically adjustable bandpass characteristics.

5 . The quantum computer hardware apparatus according to claim 1 , wherein
the coolable filter belongs to a first set of coolable filters, the second stage further includes at least one coupler connected to the superconducting qubits, and said intermediate stage further includes a second set of at least one coolable filter, each configured for thermalizing radio frequency signals transmitted to said at least one coupler.

6 . The quantum computer hardware apparatus according to claim 5 , wherein
each of the at least one coolable filter of the second set is configured as a narrowband, reflectionless bandpass filter.

7 . The quantum computer hardware apparatus according to claim 1 , wherein
said intermediate stage does not include any attenuator configured to attenuate a radio frequency signal from said signal generator.

8 . The quantum computer hardware apparatus according to claim 1 , wherein
each of said superconducting qubits is of the transmon type.

9 . The quantum computer hardware apparatus according to claim 1 , wherein
the second stage further includes at least one frequency-tunable coupling element, each coupled to two or more of the qubits.

10 . A method for thermalizing radio frequency signals in a quantum computer hardware apparatus, the method comprising:
generating radio frequency signals conveyed through a first stage of the apparatus to drive superconducting qubits arranged in a second stage, while cooling down the second stage at a lower temperature than the first stage; and at an intermediate stage between the first stage and the second stage, thermalizing the radio frequency signals generated by signal generators via a cooled filter arranged in said intermediate stage, wherein the cooled filter is configured as a reflectionless bandpass filter, said radio frequency signals being thermalized by allowing a signal inside a passband of said cooled filter while absorbing a signal in a stopband of said filter.

11 . The method according to claim 10 , wherein
the apparatus comprises several intermediate stages, the several intermediate stages including at least said intermediate stage, wherein the several intermediate stages are arranged between the first stage and the second stage, so as for the first stage, the intermediate stages, and the second stage to form a series of stages, and wherein each of the several intermediate stages comprises a cooled filter, and the method comprises, while generating said radio frequency signals, cooling down each of the intermediate stages at a lower temperature than any previous stage in the series, and thermalizing said radio frequency signals throughout the intermediate stages via the cooled filter thereof.

12 . The method according to claim 10 , wherein the method further comprises
cooling down the first stage at a temperature between 2 and 6 Kelvin, while cooling down the second stage at a lower temperature than the first stage.

13 . The method according to claim 10 , wherein the method further comprises
dynamically adjusting bandpass characteristics of the cooled filter arranged in the intermediate stage.

14 . The method according to claim 10 , wherein
said cooled filter belongs to a first set of cooled filters, the second stage further includes at least one coupler connected to the superconducting qubits, and said intermediate stage further includes a second set of at least one cooled filter, the method further including, at said intermediate stage, thermalizing radio frequency signals transmitted to said at least one coupler via the second set of at least one cooled filter.

15 . The method according to claim 14 , wherein
each of the at least one cooled filter of the second set is configured as a narrowband reflectionless bandpass filter.

16 . A quantum computer hardware apparatus, comprising:
a first stage connected to a signal generator; a second stage with superconducting qubits arranged therein, the second stage adapted to be cooled down at a lower temperature than the first stage, wherein the signal generator is configured to generate radio frequency signals to drive the qubits; and an intermediate stage between the first stage and the second stage, wherein the intermediate stage comprises at least a coolable filter, the coolable filter configured for thermalizing radio frequency signals from the signal generator, wherein the coolable filter belongs to a first set of coolable filters, the second stage further includes at least one coupler connected to the superconducting qubits, and said intermediate stage further includes a second set of at least one coolable filter, each configured for thermalizing radio frequency signals transmitted to said at least one coupler.

17 . The quantum computer hardware apparatus of claim 16 , wherein
each of the at least one coolable filter of the second set is configured as a narrowband, reflectionless bandpass filter.

18 . The quantum computer hardware apparatus of claim 16 , wherein
said intermediate stage does not include any attenuator configured to attenuate a radio frequency signal from said signal generator.

19 . The quantum computer hardware apparatus of claim 16 , wherein
each of said superconducting qubits is of the transmon type.

20 . The quantum computer hardware apparatus of claim 16 , wherein
the second stage further includes at least one frequency-tunable coupling element, each coupled to two or more of the qubits.

Assignees

• IBM

Inventors

• Mueller Peter
• Morf Thomas

Classifications

• H03H11/54 Primary

  Modifications of networks to reduce influence of variations of temperature · CPC title

• H03K17/92

  by the use, as active elements, of superconductive devices · CPC title

• G06N10/00 Primary

  Quantum computing, i.e. information processing based on quantum-mechanical phenomena · CPC title

• H03F19/00 Primary

  Amplifiers using superconductivity effects · CPC title

• H03H11/04

  Frequency selective two-port networks · CPC title