Driving dark modes to facilitate entanglement
View Patent ↗Systems and techniques that facilitate entanglement via driving dark modes are provided. In various embodiments, a method can comprise accessing a first multi-mode qubit and a second multi-mode qubit. In various cases, the first multi-mode qubit can be coupled to the second multi-mode qubit by a mode-selective coupler. In various aspects, the method can further comprise exciting a dark mode of the first multi-mode qubit. In various cases, the exciting the dark mode can entangle the first multi-mode qubit with the second multi-mode qubit.
1. A method, comprising:
accessing a first multi-mode qubit that is coupled by a mode-selective coupler to a second multi-mode qubit; and
exciting a dark mode of the first multi-mode qubit, wherein the exciting the dark mode entangles the first multi-mode qubit with the second multi-mode qubit.
2. The method of claim 1 , wherein the exciting the dark mode of the first multi-mode qubit comprises:
applying a pi-pulse to the first multi-mode qubit.
3. The method of claim 2 , wherein the exciting the dark mode of the first multi-mode qubit further comprises:
idling for a predetermined time period after the applying the pi-pulse; and
applying a negative pi-pulse to the first multi-mode qubit based on the predetermined time period elapsing.
4. The method of claim 3 , wherein the mode-selective coupler couples the dark mode of the first multi-mode qubit to another dark mode of the second multi-mode qubit, and wherein the mode-selective coupler leaves a bright mode of the first multi-mode qubit uncoupled from another bright mode of the second multi-mode qubit.
5. The method of claim 4 , wherein the first multi-mode qubit and the second multi-mode qubit are two-junction transmon qubits.
6. The method of claim 5 , wherein the mode-selective coupler is a capacitor that directly couples a middle capacitor pad of the first multi-mode qubit to another middle capacitor pad of the second multi-mode qubit.
7. The method of claim 5 , wherein the mode-selective coupler is a bus resonator that capacitively couples a middle capacitor pad of the first multi-mode qubit to another middle capacitor pad of the second multi-mode qubit.
8. The method of claim 3 , further comprising:
applying an echo pi-pulse to a third multi-mode qubit that is coupled to the first multi-mode qubit.
9. A device, comprising:
a first multi-mode qubit and a second multi-mode qubit; and
a mode-selective coupler that couples the first multi-mode qubit to the second multi-mode qubit, wherein the mode-selective coupler is configured to, upon excitation of a dark mode of the first multi-mode qubit, entangle the first multi-mode qubit with the second multi-mode qubit.
10. The device of claim 9 , wherein the dark mode of the first multi-mode qubit is excited via application of a pi-pulse to the first multi-mode qubit.
11. The device of claim 10 , wherein the dark mode of the first multi-mode qubit is de-excited via application of a negative pi-pulse to the first multi-mode qubit, and wherein the negative pi-pulse is applied after a predetermined time period has elapsed following the application of the pi-pulse.
12. The device of claim 11 , wherein the mode-selective coupler couples the dark mode of the first multi-mode qubit to another dark mode of the second multi-mode qubit, and wherein the mode-selective coupler leaves a bright mode of the first multi-mode qubit uncoupled from another bright mode of the second multi-mode qubit.
13. The device of claim 12 , wherein the first multi-mode qubit and the second multi-mode qubit are two-junction transmon qubits.
14. The device of claim 13 , wherein the mode-selective coupler is a capacitor that directly couples a middle capacitor pad of the first multi-mode qubit to another middle capacitor pad of the second multi-mode qubit.
15. The device of claim 13 , wherein the mode-selective coupler is a bus resonator that capacitively couples a middle capacitor pad of the first multi-mode qubit to another middle capacitor pad of the second multi-mode qubit.
16. The device of claim 11 , further comprising:
a third multi-mode qubit that is coupled to the first multi-mode qubit, wherein an echo pi-pulse is applied to the third multi-mode qubit.
17. A method, comprising:
accessing a first two-junction transmon qubit and a second two-junction transmon qubit, wherein a middle capacitor pad of the first two-junction transmon qubit is capacitively coupled to another middle capacitor pad of the second two-junction transmon qubit; and
entangling the first two-junction transmon qubit with the second two-junction transmon qubit, by driving the first two-junction transmon qubit with a dark mode excitation pulse sequence.
18. The method of claim 17 , wherein the middle capacitor pad of the first two-junction transmon qubit being capacitively coupled to the another middle capacitor pad of the second two-junction transmon qubit causes the dark mode of the first two-junction transmon qubit to be coupled to another dark mode of the second two-junction transmon qubit, and wherein the middle capacitor pad of the first two-junction transmon qubit being capacitively coupled to the another middle capacitor pad of the second two-junction transmon qubit causes a bright mode of the first two-junction transmon qubit to remain uncoupled from another bright mode of the second two-junction transmon qubit.
19. The method of claim 17 , wherein the dark mode excitation pulse sequence includes a first pi-pulse, a first idle time, and a first negative pi-pulse.
20. The method of claim 19 , wherein the dark mode excitation pulse sequence further includes a second pi-pulse, a second idle time, and a second negative pi-pulse, wherein the first negative pi-pulse and the second pi-pulse are separated by an echo pi-pulse applied to a third two-junction transmon qubit that is coupled to the first two-junction transmon qubit.