Tunable quantum logic gate on photonic qubits with a ladder emitter

TL;DR

This paper proposes a passive, deterministic quantum logic gate for photonic qubits using a cascade emitter, enabling tunable controlled-phase operations without active control, which could improve quantum circuit efficiency.

Contribution

It introduces a novel scheme for a tunable, passive controlled-phase gate on photonic qubits using a cascade emitter with frequency detuning control.

Findings

Enables controlled-phase operations from 0 to π.

Requires only a single cascade emitter, reducing complexity.

Does not need active control, improving efficiency.

Abstract

We present a scheme to implement a passive and deterministic controlled-variable phase gate on photonic qubits encoded in the frequency basis. Our gate employs a cascade system with the ground to first excited state interacting with the control photon of a given polarization, and the first to second excited state transition interacting with the target photon of the orthogonal polarization. By controlling the relative detuning between the target photon and the frequency of the transition between the first and second excited states of the cascade emitter, we enable any controlled-phase operation from 0 to $\pi$. This gate does not utilize any active control and needs only a single cascade emitter, enabling low-footprint and more efficient decomposition of quantum circuits, especially those rooted in the quantum Fourier transform.