Parametrically activated quantum logic gates

Patent metadata

Field	Value
Publication number	US-11677402-B2
Application number	US-202117410042-A
Country	US
Kind code	B2
Filing date	Aug 24, 2021
Priority date	Jun 19, 2017
Publication date	Jun 13, 2023
Grant date	Jun 13, 2023

Abstract

In a general aspect, a quantum logic gate is performed in a quantum computing system. In some cases, a pair of qubits are defined in a quantum processor; the pair of qubits can include a first qubit defined by a first qubit device in the quantum processor and a second qubit defined by a tunable qubit device in the quantum processor. A quantum logic gate can be applied to the pair of qubits by communicating a control signal to a control line coupled to the tunable qubit device. The control signal can be configured to modulate a transition frequency of the tunable qubit device at a modulation frequency, and the modulation frequency can be determined based on a transition frequency of the first qubit device.

First claim

What is claimed is:

1. A quantum information control method comprising:
generating a control signal configured to modulate, at a modulation frequency, a transition frequency of a tunable qubit device in a quantum processor, the modulation frequency being determined based on a transition frequency of a fixed-frequency qubit device in the quantum processor, the transition frequency of the fixed-frequency qubit device being independent of a magnetic flux experienced by the fixed-frequency qubit device; and
applying a two-qubit quantum logic gate to a pair of qubits in the quantum processor by communicating the control signal to a control line coupled to the tunable qubit device, the pair of qubits comprising a first qubit defined by the fixed-frequency qubit device and a second qubit defined by the tunable qubit device,
wherein applying the two-qubit quantum logic gate to the pair of qubits comprises one of the following:
applying an iSWAP gate to the pair of qubits;
applying a square-root-of-iSWAP gate to the pair of qubits;
applying a controlled-Z gate to the pair of qubits; or
applying a Bell-Rabi gate to the pair of qubits.

2. The method of claim 1 , comprising determining the modulation frequency based on the sum or the difference of:
the transition frequency of the tunable qubit device, and
the transition frequency of the fixed-frequency qubit device.

3. The method of claim 1 , wherein the modulation frequency is determined based on the transition frequency of the fixed-frequency qubit device and the transition frequency of the tunable qubit device.

4. The method of claim 1 , wherein the modulation frequency is determined based on the transition frequency of the fixed-frequency qubit device and the anharmonicity of the tunable qubit device.

5. The method of claim 1 , wherein the modulation frequency is determined based on the transition frequency between the ground state and first excited state of the fixed-frequency qubit device.

6. The method of claim 1 , wherein the modulation frequency is determined based on the transition frequency between the first excited state and second excited state of the fixed-frequency qubit device.

7. The method of claim 1 , wherein applying the two-qubit quantum logic gate to the pair of qubits comprises applying an iSWAP gate to the pair of qubits.

8. The method of claim 7 , wherein the control signal is configured to modulate the transition frequency of the tunable qubit device at the modulation frequency with a modulation amplitude ow, and the control signal is configured to produce an interaction between the tunable qubit device and the fixed-frequency qubit device for a total interaction time

t

i
⁢
S
⁢
W
⁢
A
⁢
P

(
1
)

=

π
2

⁢

1

g
|

J
1

⁡

(

δ
⁢

ω
/

ω
m

)

|

,

where g represents a capacitive coupling strength between the tunable qubit device and the fixed-frequency qubit device, J 1 represents a first-order Bessel function of the first kind, and ω m represents the modulation frequency.

9. The method of claim 1 , wherein applying the two-qubit quantum logic gate to the pair of qubits comprises applying a square-root-of-iSWAP gate to the pair of qubits.

10. The method of claim 9 , wherein the control signal is configured to modulate the transition frequency of the tunable qubit device at the modulation frequency with a modulation amplitude ow, and the control signal is configured to produce an interaction between the tunable qubit device and the fixed-frequency qubit device for a total interaction time

t

i
⁢
S
⁢
W
⁢
A
⁢
P

(
1
)

=

π
4

⁢

1

g
⁢



J
1

⁡

(

δ
⁢

ω
/

ω
m

,

)



,

where g represents a capacitive coupling strength between the tunable qubit device and the fixed-frequency qubit device, J 1 represents a first-order Bessel function of the first kind, and ω m represents the modulation frequency.

11. The method of claim 1 , comprising generating the control signal to modulate the transition frequency of the tunable qubit device about a reference frequency ω T 01 at the modulation frequency ω m =| ω T 01 −ω F 01 |, where ω F 01 represents the transition frequency of the fixed-frequency qubit device.

12. The method of claim 1 , wherein applying the two-qubit quantum logic gate to the pair of qubits comprises applying a controlled-Z gate to the pair of qubits.

13. The method of claim

Assignees

• Rigetti & Co Llc

Inventors

• Sete Eyob A
• Didier Nicolas
• Da Silva Marcus Palmer
• Rigetti Chad Tyler
• Reagor Matthew J
• Caldwell Shane Arthur
• Tezak Nikolas Anton
• Ryan Colm Andrew
• Hong Sabrina Sae Byul
• Sivarajah Prasahnt
• Papageorge Alexander
• Abrams Deanna Margo

Classifications

• H03K19/195 Primary

  using superconductive devices · CPC title

• G06N10/00

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

• G06N10/20

  Models of quantum computing, e.g. quantum circuits or universal quantum computers · CPC title

• G06N10/70

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

• G06N10/40

  Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control · CPC title