US-20260127475-A1 - QUBIT RESET

Abstract

Various example embodiments relate to an arrangement for resetting at least one qubit. According to an embodiment, the arrangement comprises the at least one qubit, a dissipative environment, and a control unit configured to reset the at least one qubit by performing operations comprising applying a reset signal to the qubit. The reset signal is generated by amplitude modulation. The reset signal induces at least one sideband mode of the qubit. The sideband mode of the qubit overlaps with a frequency of the dissipative environment.

Inventors

• Vasili SEVRIUK
• Jami Rönkkö
• Fabian MARXER
• Antti Vepsäläinen

Assignees

• IQM FINLAND OY

Dates

Publication Date

20260507

Application Date

20230522

Priority Date

20221003

Claims (17)

1. 1 . An arrangement for resetting at least one qubit, comprising: the at least one qubit; a dissipative environment configured to dissipate energy transferred from the at least one qubit; and a control unit configured to reset the at least one qubit by performing operations comprising: applying an amplitude modulated reset signal to the qubit, wherein the amplitude modulated reset signal induces at least one sideband mode of the qubit, wherein the sideband mode of the qubit overlaps with a frequency of the dissipative environment.
2. 2 . The arrangement according to claim 1 , wherein a frequency of the sideband mode of the qubit approximatively coincides with the frequency of the dissipative environment.
3. 3 . The arrangement according to claim 2 , wherein a difference between the frequency of the sideband mode of the qubit and the frequency of the dissipative environment is less than a decay rate of the dissipative environment.
4. 4 . The arrangement according to claim 2 , wherein a difference between the frequency of the sideband mode of the qubit and the frequency of the dissipative environment is less than 10% of the frequency of the dissipative environment, or less than 20% of the frequency of the dissipative environment.
5. 5 . The arrangement according to claim 1 claim, wherein the amplitude modulated reset signal is generated by modulating an amplitude of a carrier signal, wherein the carrier signal is off-resonant with the qubit.
6. 6 . The arrangement according to claim 5 , wherein a difference between a frequency of the carrier signal and an initial frequency of the qubit is in a range of 50 to 500 MHz.
7. 7 . The arrangement according to claim 5 , wherein the amplitude modulated reset signal is generated by modulating the amplitude of the carrier signal according to a modulating signal, wherein a frequency of the modulating signal approximately coincides with a frequency difference between a frequency of a central mode of the qubit and a frequency of the dissipative environment.
8. 8 . The arrangement according to claim 1 , wherein the dissipative environment is a resonator, wherein the frequency of the dissipative environment is the frequency of a mode of resonance of the resonator.
9. 9 . The arrangement according to claim 8 , wherein the resonator is a readout resonator or an additional resonator.
10. 10 . The arrangement according to claim 1 , wherein a decay rate of the dissipative environment is in a range of 5 to 20 MHz.
11. 11 . The arrangement according to claim 1 , wherein the dissipative environment is capacitively coupled to the at least one qubit.
12. 12 . The arrangement according to claim 1 , wherein the arrangement further comprises a drive line, the at least one qubit being coupled to the drive line, and wherein applying the amplitude modulated reset signal to the qubit comprises applying a first amplitude modulated reset signal to the qubit via the drive line.
13. 13 . The arrangement according to claim 1 , wherein applying the amplitude modulated reset signal to the qubit comprises applying a second amplitude modulated reset signal to the qubit through the dissipative environment.
14. 14 . The arrangement according to claim 1 , wherein the arrangement further comprises a flux line, the at least one qubit being coupled to the flux line, and wherein the operations further comprise applying a third reset signal to the qubit through the flux line.
15. 15 . A quantum computing system comprising at least one arrangement according to claim 1 .
16. 16 . A method for resetting at least one qubit using a dissipative environment, the method comprising: applying an amplitude modulated reset signal to the qubit, wherein the amplitude modulated reset signal induces at least one sideband mode of the qubit, wherein the sideband mode of the qubit overlaps with a frequency of the dissipative environment.
17. 17 . A method according to claim 16 , wherein applying the amplitude modulated reset signal comprises one or more of: applying a first amplitude modulated reset signal to the qubit-via a drive line; or applying a second amplitude modulated reset signal to the qubit through the dissipative environment.

Description

TECHNICAL FIELD The present disclosure relates to quantum computing, and more particularly to an arrangement for resetting at least one qubit, to a method for resetting at least one qubit, and to a quantum computing system. BACKGROUND The ability to reset rapidly qubits with high fidelity is one of the prerequisites for coherent quantum computations. SUMMARY This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. According to a first aspect, an arrangement for resetting at least one qubit comprises the at least one qubit, a dissipative environment configured to dissipate energy transferred from the at least one qubit, and a control unit. The control unit is configured to reset the at least one qubit by applying an amplitude modulated reset signal to the qubit. The amplitude modulated reset signal induces at least one sideband mode of the qubit. The sideband mode of the qubit overlaps with a frequency of the dissipative environment. Some embodiments enable reset of one or more qubits, in particular tunable superconducting qubits. By applying an amplitude modulated reset signal to the qubit, a swap between the qubit and the dissipative environment is realized. As a result, the excited state population in the qubit is substantially reduced or suppressed. Some embodiments provide an unconditional reset scheme for one or more qubits. By modulating the amplitude of the reset signal of the qubit, a controllable interaction is generated between the qubit and the dissipative environment. This interaction unconditionally transfers the qubit excitation to the dissipative environment. This allows on demand reset of the qubit. Some embodiments enable fast reset with high fidelity. In some embodiments, with typical values of the sample, the reset can be achieved in less than 100 ns, with a fidelity of at least 99% or higher. In some embodiment, the reset can be achieved in less than 20 ns, with a fidelity of at least 99% or higher. Some embodiments do not require a flux line. The absence of a flux line simplifies the wiring of the quantum architecture. A flux line is a source of noise which might affect the qubit. Therefore, the absence of a flux line may reduce or suppress effects of noise on the qubit. Further, a flux line might affect neighbouring qubits via crosstalk. Therefore, the absence of a flux line may reduce or suppress effects on neighbouring qubits. Some embodiments only involve applying an amplitude modulated reset signal and do not need sophisticated calibration. Some embodiments are compatible with circuit quantum electrodynamics (circuit QED) systems and can be applied to any type of qubit which can be combined with circuit QED, including frequency-tunable superconducting qubits as well as non-tunable qubits. Some embodiments do not require any additional hardware or modifications to chip components. According to an example embodiment of the first aspect, the amplitude modulated reset signal is generated by modulating an amplitude of a carrier signal, wherein the carrier signal is off-resonant with the qubit. According to an example embodiment of the first aspect, the off-resonant carrier signal induces a shift in the frequency of the qubit by the AC Stark effect. The off-resonant carrier signal is amplitude modulated such that the amplitude of the AC Stark shift is modulated. Thus, the amplitude modulated reset signal modulates the frequency of the qubit. The modulation of the qubit frequency creates a sideband in the frequency of the qubit. The frequency of the modulation is selected such that the sideband in the frequency of the qubit overlaps with the frequency of the dissipative environment. According to an example embodiment of the first aspect, a frequency of the sideband mode of the qubit approximatively coincides with the frequency of the dissipative environment. According to an example embodiment of the first aspect, a difference between the frequency of the sideband mode of the qubit and the frequency of the dissipative environment is less than a decay rate of the dissipative environment. According to an example embodiment of the first aspect, a difference between the frequency of the sideband mode of the qubit and the frequency of the dissipative environment is less than 10% of the frequency of the dissipative environment, or less than 20% of the frequency of the dissipative environment. According to an example embodiment of the first aspect, a difference between a frequency of the carrier signal and an initial frequency of the qubit is in a range of 50 to 500 MHz. According to an example embodiment of the first aspect, the amplitude modulated reset signal is generated by modulating the amplitude of the carrier signal ac