High-fidelity quantum state control of a polar molecular ion in a cryogenic environment

TL;DR

This paper demonstrates high-fidelity quantum control of a polar molecular ion in a cryogenic environment using quantum-logic spectroscopy, achieving precise state preparation and measurement without molecule-specific lasers.

Contribution

Introduces a cryogenic quantum-logic spectroscopy protocol for polar molecules that enables non-destructive, high-fidelity quantum state control without molecule-specific lasers.

Findings

State preparation and measurement infidelity less than 0.006

Rabi flopping contrast greater than 99%

Extended rotational state lifetimes in cryogenic environment

Abstract

We use a quantum-logic spectroscopy (QLS) protocol to control the quantum state of a CaH+ ion in a cryogenic environment, in which reduced thermal radiation extends rotational state lifetimes by an order of magnitude over those at room temperature. By repeatedly and adaptively probing the molecule, detecting the outcome of each probe via an atomic ion, and using a Bayesian update scheme to quantify confidence in the molecular state, we demonstrate state preparation and measurement (SPAM) in a single quantum state with infidelity less than 6x10^-3 and measure Rabi flopping between two states with greater than 99% contrast. The protocol does not require any molecule-specific lasers and the detection scheme is non-destructive.