Individual qubit excitation control
Methods, systems, and apparatus for individual qubit excitation control. In one aspect, a method includes accessing a quantum system that comprises a plurality of qubits; a plurality of qubit frequency control lines, each qubit frequency control line corresponding to an individual qubit and controlling the frequency of the qubit; a driveline; a plurality of couplers, each coupler coupling a corresponding qubit to the driveline so that a plurality of qubits are coupled to the driveline; determining one or more qubits that require a rotation operation; for each qubit requiring a rotation operation: tuning the qubit frequency to the corresponding driveline frequency of the rotation operation; performing the rotation operation using a microwave pulse on the excitation drive; and tuning the qubit away from the driveline frequency of the rotation operation.
1. An apparatus, comprising:
a plurality of qubits;
a plurality of qubit frequency control lines, each qubit frequency control line corresponding to an individual qubit and controlling the frequency of the qubit;
a driveline;
a plurality of couplers, each coupler coupling a corresponding qubit to the driveline so that a plurality of qubits are coupled to the driveline.
2. The apparatus of claim 1 , further comprising a qubit controller that is configured to:
generate excitation pulses on the driveline, each pulse corresponding to one of a plurality of quantum gate frequencies for a respective plurality of quantum gates;
control individual frequencies of the plurality of qubits using the qubit frequency control lines so that, for each qubit, the qubit frequency is adjusted towards or away from a quantum gate frequency of a current pulse on the driveline.
3. The apparatus of claim 2 , wherein the qubit controller is configured to:
determine one or more qubits that require a rotation operation;
for each qubit requiring a rotation operation:
tune the qubit frequency to a corresponding gate frequency of the rotation operation; and
perform the rotation operation using a microwave pulse on the driveline.
4. The apparatus of claim 1 , wherein the plurality of couplers are of equal or highly similar strength.
5. The apparatus of claim 1 , wherein each of the plurality of qubits is coupled to an equal or highly similar length of the driveline.
6. The apparatus of claim 1 , wherein the plurality of qubits are dissimilarly coupled to the driveline.
7. The apparatus of claim 2 , wherein the plurality of quantum gates include n and n/2 rotation gates about the X and Y axis.
8. The apparatus of claim 1 , wherein a wiring of the individual qubit frequency control lines is supplied by in-plane wiring.
9. The apparatus of claim 1 , wherein a wiring of the individual qubit frequency control lines is supplied by out-plane wiring.
10. A method for individual qubit excitation control, comprising:
accessing a quantum system that comprises:
a plurality of qubits;
a plurality of qubit frequency control lines, each qubit frequency control line corresponding to an individual qubit and controlling the frequency of the qubit;
a driveline;
a plurality of couplers, each coupler coupling a corresponding qubit to the driveline so that a plurality of qubits are coupled to the driveline;
determining one or more qubits that require a rotation operation;
for each qubit requiring a rotation operation:
tuning the qubit frequency to the corresponding driveline frequency of the rotation operation;
performing the rotation operation using a microwave pulse on the driveline;
tuning the qubit away from the driveline frequency of the rotation operation.
11. The method of claim 10 , wherein tuning the qubit frequency to the corresponding driveline frequency of the rotation operation is performed by a rounded rectangular pulse.
12. The method of claim 10 , wherein the microwave pulse on the driveline has a shaped envelope.
13. The method of claim 10 , wherein different rotations are simultaneously performed on different qubits.
14. The method of claim 13 , wherein the different rotations simultaneously performed on the different qubits are performed using frequency domain multiplexing and qubit frequency tuning.
15. The method of claim 10 , wherein the microwave pulse is a single microwave pulse.
16. The method of claim 10 , wherein the microwave pulse comprises multiple microwave pulses.
17. The method of claim 10 , wherein tuning the qubit away from the driveline frequency of the rotation operation is performed before a next pulse is applied to the driveline.
18. The method of claim 10 , wherein the quantum system further comprises a qubit controller that:
generates excitation pulses on the driveline, each pulse corresponding to one of a plurality of quantum gate frequencies for a respective plurality of quantum gates;
controls individual frequencies of the plurality of qubits using the qubit frequency control lines so that, for each qubit, the qubit frequency is adjusted towards or away from a quantum gate frequency of a current pulse on the driveline.
19. The method of claim 18 , wherein the qubit controller:
determines one or more qubits that require a rotation operation;
for each qubit requiring a rotation operation:
tunes the qubit frequency to a corresponding gate frequency of the rotation operation; and
performs the rotation operation using a microwave pulse on the driveline.
20. The method of claim 18 , wherein the plurality of quantum gates include n and n/2 rotation gates about the X and Y axis.