Overcoming experimental limitations in a non-linear two-qubit gate through postselection

TL;DR

This paper presents a modular two-qubit gate leveraging postselection to overcome experimental limitations, enabling probabilistic amplification of phase shifts while reducing absorption effects in quantum systems.

Contribution

It introduces a novel modular-value two-qubit gate that uses pre- and post-selection to enhance performance under experimental constraints.

Findings

Probabilistic amplification of small cross phase shifts achieved

Mitigation of undesired absorption effects demonstrated

Emergence of complementary behavior between phase and amplitude

Abstract

We introduce a modular-value two-qubit gate and explore its advantages in experimentally-limited situations. The gate is defined such that the final state of a target qubit is fully controlled by a pre- and post-selection procedure in a control qubit given an (imperfect or technically limited) intermediate conditional qubit-qubit interaction. As an example of the gate and its benefit, we make the connection to a postselected cross phase modulation scenario when a undesired absorption is present. Probabilistic amplification of a small cross phase while mitigating relative absorption is possible, and a complementary behaviour between phase and amplitude emerges.