A new binary-search approach to optical quantum metrology

Neil B. Lovett, Cécile Crosnier de Bellaistre, Martí Perarnau-Llobet +1 more

We devise powerful algorithms based on differential evolution for adaptive many-particle quantum metrology. Our new approach delivers adaptive quantum metrology policies for feedback control that are orders-of-magnitude more efficient and surpass the few-dozen-particle limitation arising in methods based on particle-swarm optimization. We apply our method to the binary-decision-tree model for quantum-enhanced phase estimation as well as to a new problem: a decision tree for adaptive estimation of the unknown bias of a quantum coin in a quantum walk and show how this latter case can be realized experimentally.

A. P. Alodjants, Dmitriy V. Tsarev, Dmitry Kuts +2 more

Mateusz Borkowski, Emily Tiberi, Brandon Iritani +4 more

Ultracold molecules are a powerful platform for metrology, precision measurements and searches for new, beyond-the-Standard-Model physics. Sr2, thanks to its simple structure, insensitivity to external fields and narrow optical transitions, provides an excellent testbed for the search for new interactions. Here, we present a detailed characterization of our 88Sr2 molecular clock for a vibrational transition spanning the entire depth of the ground state potential. We also discuss prospects to use strontium isotopologues to place improved constraints on new mass-dependent forces, including possible pathways toward the production of ultracold 86Sr2 and 84Sr2 dimers and spectroscopy of clock lines in these species for use in the search for new mass-dependent forces.

A. P. Alodjants, Dmitriy V. Tsarev, Dmitry Kuts +2 more

V. V. Zemlyanov, N. S. Kirsanov, Michael Romanovich Perelshtein +5 more

P A Knott

In this paper we present a search algorithm that finds useful optical quantum states which can be created with current technology. We apply the algorithm to the field of quantum metrology with the goal of finding states that can measure a phase shift to a high precision. Our algorithm efficiently produces a number of novel solutions: we find experimentally ready schemes to produce states that show significant improvements over the state-of-the-art, and can measure with a precision that beats the shot noise limit by over a factor of 4. Furthermore, these states demonstrate a robustness to moderate/high photon losses, and we present a conceptually simple measurement scheme that saturates the Cramér–Rao bound.