US 12,689,373 B2Granted

Universal fast-flux control of low-frequency qubits

AssigneeThe University of Chicago

InventorsDavid I. Schuster, Helin Zhang

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Abstract

Methods for initializing a qubit into a pure state, reading the qubit, and arbitrarily rotating the qubit into any quantum state complete in times shorter than the qubit's typical dephasing and relaxation times. These methods provide universal single-qubit control and may be used to implement quantum gates with high fidelity. The methods may be implemented with superconducting qubits, such as heavy fluxonium, and do not rely on a three-dimensional cavity for suppressing spontaneous emission. Therefore, the methods may be implemented using smaller two-dimensional architectures commonly used for superconducting circuits. The methods also work with low-frequency qubits, i.e., qubits for which the energy spacing between the two quantum-computational states is less than the mean thermal energy of a surrounding bath. This reduces the cooling requirements of the qubit while maintaining fidelity.

Claims17

Dependent claims

A method for initializing a quantum system formed from a qubit coupled to an energy dissipater, the qubit having a qubit ground state, a qubit metastable state, a first qubit excited state having a first excited-state energy, and a second qubit excited state having a second qubit-excited energy that is greater than the first excited-state energy, said method comprising:

exciting the quantum system from a first quantum state to a second quantum state by resonantly driving the quantum system with a first oscillating electromagnetic field, the first quantum state being a composite of the qubit ground state and a dissipater ground state of the energy dissipater, the second quantum state being a composite of the second qubit excited state and the dissipater ground state;
and
coupling the quantum system from the second quantum state to a third quantum state by resonantly driving the quantum system with a second oscillating electromagnetic field, the third quantum state being a composite of the qubit metastable state and a dissipater excited state of the energy dissipater;
wherein the quantum system decays from the third quantum state to a fourth quantum state that is a composite of the qubit metastable state and the dissipater ground state.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 17/904,377Filed 17 Feb 2021 · us provisional application
Priority: 18 Feb 2020
Published: US 2023/0073224 A19 Mar 2023
Granted: 21 Jul 2026
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H03K 17/92
Characterised by the components used: by the use, as active elements, of superconductive devices
G06N 10/40
Quantum computing, i.e. information processing based on quantum-mechanical phenomena: physical realisations or architectures of quantum processors…
G06N 10/60
Quantum computing, i.e. information processing based on quantum-mechanical phenomena: quantum algorithms, e.g. based on quantum optimisation,…
G06N 10/70
Quantum computing, i.e. information processing based on quantum-mechanical phenomena: quantum error correction, detection or prevention, e.g.…