Cavity State Manipulation Using Photon-Number Selective Phase Gates

TL;DR

This paper introduces the SNAP gate, a method for selectively controlling quantum phases in cavity resonators, enabling scalable quantum operations on oscillator-encoded qubits with high fidelity.

Contribution

The paper presents the SNAP gate, a novel technique for applying photon-number selective phase shifts, facilitating complex quantum control in cavity resonators.

Findings

SNAP gate imparts different phases to Fock states using an off-resonant qubit.

Combining SNAP with displacements creates high-fidelity one-photon Fock states.

The approach enables arbitrary unitary operations on oscillator-encoded qubits.

Abstract

The large available Hilbert space and high coherence of cavity resonators makes these systems an interesting resource for storing encoded quantum bits. To perform a quantum gate on this encoded information, however, complex nonlinear operations must be applied to the many levels of the oscillator simultaneously. In this work, we introduce the Selective Number-dependent Arbitrary Phase (SNAP) gate, which imparts a different phase to each Fock state component using an off-resonantly coupled qubit. We show that the SNAP gate allows control over the quantum phases by correcting the unwanted phase evolution due to the Kerr effect. Furthermore, by combining the SNAP gate with oscillator displacements, we create a one-photon Fock state with high fidelity. Using just these two controls, one can construct arbitrary unitary operations, offering a scalable route to performing logical manipulations on oscillator-encoded qubits.