Quantum-circuit guide to optical and atomic interferometry

TL;DR

This paper unifies atomic and optical interferometry protocols using quantum circuit diagrams, demonstrating equivalences and converting Fock-state protocols into more experimentally feasible entangled coherent-state protocols.

Contribution

It introduces a unified quantum circuit framework for phase estimation, showing equivalences and practical conversions between different quantum states for interferometry.

Findings

Demonstrates circuit equivalences for Heisenberg-limited protocols

Converts Fock-state superpositions to entangled coherent states

Protocols are more feasible for laboratory implementation

Abstract

Atomic (qubit) and optical or microwave (modal) phase-estimation protocols are placed on the same footing in terms of quantum-circuit diagrams. Circuit equivalences are used to demonstrate the equivalence of protocols that achieve the Heisenberg limit by employing entangled superpositions of Fock states, such as N00N states. The key equivalences are those that disentangle a circuit so that phase information is written exclusively on a mode or modes or on a qubit. The Fock-state-superposition phase-estimation circuits are converted to use entangled coherent-state superpositions; the resulting protocols are more amenable to realization in the lab, particularly in a qubit/cavity setting at microwave frequencies.