Entanglement-Enhanced Matter-Wave Interferometry

Using cavity quantum electrodynamics, I have explored interactions between light and matter. In one set of experiments, collective measurements of atomic ensembles of 87Rb atoms are used to generate large amounts of spin-squeezing in a proof-of-principle quantum sensor. These correlations between atoms are a fundamental quantum resource, capable of improving sensor resolution beyond the limits set by individual particle wavefunction collapse. Strong atom-light coupling and quantum non-demolition measurements enable an unprecedented factor of 60 in directly observed phase enhancement beyond the standard quantum limit. These techniques are extended to generate deterministic squeezed states using real-time feedback and homogeneously entangled ensembles guided along the cavity.

In a second set of experiments, momentum-squeezed states are generated by the two most successful cavity-mediated approaches to entanglement: quantum non-demolition measurements and one-axis twisting. Said states are inserted into the first Mach-Zehnder light-pulse matter-wave interferometer with metrological enhancement due to entanglement. In this sensor, free-falling atoms simultaneously traverse two paths through space while also entangled with each other, exploiting the many-body nature of the system. Both Raman and Bragg transitions are used to coherently manipulate matter-waves along the cavity axis, providing sensitivity to gravity. These experiments set a path for a future generation of quantum-enhanced sensors engaging in applied and fundamental physics.

Along the way, we have developed new techniques with potential for broad impacts on physics. These include experiments demonstrating a novel laser cooling mechanism based on Raman adiabatic passage and an atom-loading protocol which maximizes coupling to an intracavity standing wave; methods for driving higher-order transverse cavity modes, generating axially- iii smooth intracavity potentials, and narrowing laser linewidths with external optical feedback; and a proposal for continuous real-time tracking of a quantum phase – a fundamentally new capability for precision metrology.