Individual qubit excitation control with a global excitation drive
Methods, systems, and apparatus for individual qubit excitation control with a global excitation drive. 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. A method for individual qubit excitation control, comprising:
for a qubit of multiple qubits that are coupled to a common driveline:
tuning a frequency of the qubit to a frequency of a rotation operation on the common driveline using a rounded rectangular pulse;
performing the rotation operation using a microwave pulse on the common driveline, wherein the microwave pulse on the common driveline has a shaped envelope; and
tuning the frequency of the qubit away from the frequency of the rotation operation.
2. The method of claim 1 , wherein different rotation operations are simultaneously performed on the multiple qubits.
3. The method of claim 2 , wherein the different rotation operations are performed using frequency domain multiplexing and qubit frequency tuning.
4. The method of claim 1 , wherein tuning the frequency of the qubit away from the frequency of the rotation operation is performed before a next pulse is applied to the common driveline.
5. The method of claim 1 , wherein the microwave pulse is a single microwave pulse.
6. The method of claim 1 , wherein the microwave pulse comprises multiple microwave pulses.
7. The method of claim 1 , further comprising:
generating excitation pulses on the common driveline, each pulse corresponding to one of a plurality of quantum gate frequencies for a respective plurality of quantum gates;
controlling individual frequencies of the multiple qubits using qubit frequency control lines so that, for each qubit of the multiple qubits, the qubit frequency is adjusted towards or away from a quantum gate frequency of a current pulse on the driveline.
8. The method of claim 7 , further comprising:
determining one or more qubits of the multiple qubits that require a rotation operation;
for each qubit requiring a rotation operation:
tuning the qubit frequency to a corresponding gate frequency of the rotation operation; and
performing the rotation operation using a microwave pulse on the common driveline, wherein the microwave pulse on the common driveline has a shaped envelope.
9. The method of claim 1 , wherein the rotation operation comprises a quantum logic gate.
10. The method of claim 9 , wherein the quantum logic gate comprises a π or π/2 rotation about the X or Y axis of the Bloch sphere.
11. An apparatus, comprising:
multiple 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 common driveline; and
a plurality of couplers, each coupler coupling a corresponding qubit to the common driveline so that a plurality of qubits are coupled to the driveline,
wherein the apparatus is configured to, for a qubit of the plurality of qubits:
tune a frequency of the qubit to a frequency of a rotation operation on the common driveline using a rounded rectangular pulse;
perform the rotation operation using a microwave pulse on the common driveline, wherein the microwave pulse on the common driveline has a shaped envelope; and
tune the frequency of the qubit away from the frequency of the rotation operation.
12. The apparatus of claim 11 , wherein different rotation operations are simultaneously performed on the multiple qubits.
13. The apparatus of claim 12 , wherein the different rotation operations are performed using frequency domain multiplexing and qubit frequency tuning.
14. The apparatus of claim 11 , wherein tuning the frequency of the qubit away from the frequency of the rotation operation is performed before a next pulse is applied to the common driveline.
15. The apparatus of claim 11 , wherein the microwave pulse is a single microwave pulse.
16. The apparatus of claim 11 , wherein the microwave pulse comprises multiple microwave pulses.
17. The apparatus of claim 1 , wherein the apparatus is further configured to:
generate excitation pulses on the common 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 multiple qubits using qubit frequency control lines so that, for each qubit of the multiple qubits, the qubit frequency is adjusted towards or away from a quantum gate frequency of a current pulse on the driveline.
18. The apparatus of claim 7 , wherein the apparatus is further configured to:
determine one or more qubits of the multiple 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 common driveline, wherein the microwave pulse on the common driveline has a shaped envelope.
19. The apparatus of claim 11 , wherein the rotation operation comprises a quantum logic gate.
20. The apparatus of claim 19 , wherein the quantum logic gate comprises a π or π/2 rotation about the X or Y axis of the Bloch sphere.