Qubit leakage error reduction

Patent metadata

Field	Value
Publication number	US-11456741-B2
Application number	US-202017107262-A
Country	US
Kind code	B2
Filing date	Nov 30, 2020
Priority date	Jul 7, 2020
Publication date	Sep 27, 2022
Grant date	Sep 27, 2022

Abstract

It is an objective to provide an arrangement for reducing qubit leakage errors in a quantum computing system. According to an embodiment, an arrangement for reducing qubit leakage errors includes a first qubit and a second qubit selectively couplable to each other. The arrangement also includes an energy dissipation structure that is selectively couplable to the first qubit. The energy dissipation structure is configured to dissipate energy transferred from the first qubit. The arrangement further includes a control unit configured to perform a first quantum operation to transfer a property of a quantum state from the first qubit to the second qubit, couple the first qubit to the energy dissipation structure for a time interval, and perform a second quantum operation to transfer the property of the quantum state from the second qubit to the first qubit after the time interval.

First claim

The invention claimed is:

1. An apparatus for reducing qubit leakage errors comprising:
a first qubit and a second qubit selectively couplable to each other;
a first energy dissipation structure selectively couplable to the first qubit and configured to dissipate energy transferred to the first energy dissipation structure; and
a control unit configured to:
perform a first quantum operation to transfer at least one property of a quantum state from the first qubit to the second qubit,
couple the first qubit to the first energy dissipation structure for a time interval, and
perform a second quantum operation to transfer the at least one property of the quantum state from the second qubit to the first qubit after the time interval.

2. The apparatus according to claim 1 , further comprising a second energy dissipation structure selectively couplable to the second qubit and configured to dissipate energy transferred to the second energy dissipation structure.

3. The apparatus according to claim 2 , wherein the control unit is further configured to initialize the second qubit to a ground state by coupling the second qubit to the second energy dissipation structure before performing the first quantum operation.

4. The apparatus according to claim 2 , wherein the control unit is further configured to initialize the second qubit to a ground state by coupling the second qubit to the second energy dissipation structure after performing the second quantum operation.

5. The apparatus according to claim 2 , wherein at least one of the first energy dissipation structure or the second energy dissipation structure includes at least one normal metal—insulator — superconductor (NIS) junction.

6. The apparatus according to claim 1 , wherein at least one of the first energy dissipation structure or the second energy dissipation structure includes a quantum circuit refrigerator (QCR), wherein the QCR includes a voltage-biased superconductor—insulator — normal metal—insulator — superconductor (SINIS) junction.

7. The apparatus according to claim 6 , wherein the first qubit is electrically coupled to the normal metal of the SINIS junction of the first energy dissipation structure.

8. The apparatus according to claim 6 , wherein the second qubit is electrically coupled to the normal metal of the SINIS junction of the second energy dissipation structure.

9. The apparatus according to claim 6 , wherein the control unit is configured to couple the first qubit to the first energy dissipation structure for the time interval by tuning a bias voltage of the SINIS junction of the first energy dissipation structure.

10. The apparatus according to claim 6 , wherein at least one of the first energy dissipation structure or the second energy dissipation structure is configured to dissipate photon energy transferred to the respective energy dissipation structure via photon-assisted electron tunnelling in the SINIS junction.

11. The apparatus according to claim 1 , wherein at least one of the first qubit or the second qubit includes a superconductive qubit.

12. The apparatus according to claim 1 , wherein at least one of the first qubit or the second qubit includes a transmon qubit.

13. The apparatus according to claim 1 , wherein the control unit is configured to perform at least one of the first quantum operation or the second quantum operation by performing a SWAP or iSWAP operation between the first qubit and the second qubit.

14. The apparatus according to claim 1 , wherein the control unit is configured to perform at least one of the first quantum operation or the second quantum operation by bringing the first qubit and the second qubit into resonance via shifting a resonance frequency of at least one of the first qubit or second qubit.

15. The apparatus according to claim 14 , wherein the control unit is configured to shift the resonance frequency of the at least one of the first qubit or second qubit via flux tuning.

16. The apparatus according to claim 1 , further comprising:
a first plurality qubits including the first qubit;
a second plurality of qubits including the second qubit, wherein each qubit in the second plurality of qubits is selectively couplable to a corresponding qubit in the first plurality of qubits; and
a plurality of energy dissipation structures including the first energy dissipation structure, wherein each energy dissipation structure in the plurality of energy dissipation structures is selectively couplable to a corresponding qubit in the first plurality of qubits, and wherein each energy dissipation structure in the plurality of energy dissipation structures is configured to dissipate energy transferred to that energy dissipation structure.

17. The apparatus according to claim 16 , wherein the control unit is further configured to:
perform the first quantum operation to transfer the at least one property of the quantum state from each qubit in the first plurality of qubits to a corresponding qubit in the second plurality of qubits;
couple each qubit in the first plurality of qubits to a corresponding energy dissipation structure in the plurality of energy dissipation structures for the time interval; and
perform the second quantum operation to transfer the at least one property of the quantum state from each qubit in the second plurality of qubits to the corresponding qubit in the first plurality of qubits.

18. A quantum computing system comprising the apparatus according to claim 1 .

19. A method for reducing qubit leakage errors comprising:
performing a first quantum operation to transfer at least one property of a quantum state from a first qubit to a second qubit;
coupling the first qubit to an energy dissipation structure for a time interval; and
performing a second quantum operation to transfer the at least one property of the quantum state from the second qubit to the first qubit after the time interval.

20. A computer program product comprising program code configured to perform the method according to claim 19 when the computer program product is executed on a computer.

Assignees

• Iqm Finland Oy

Inventors

• Ahonen Olli
• Heinsoo Johannes
• Möttönen Mikko
• Rönkkö Jami
• Salo Jaakko
• Tuorila Jani

Classifications

• H03H11/04

  Frequency selective two-port networks · CPC title

• H03K19/00346 Primary

  Modifications for eliminating interference or parasitic voltages or currents · CPC title

• H01L39/223

  Electricity · mapped topic

• G06N10/00

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

• G06N10/70 Primary

  Quantum error correction, detection or prevention, e.g. surface codes or magic state distillation · CPC title