A promising form of near-term quantum technologies are quantum-enhanced sensors, which use entanglement and quantum correlations to surpass the standard quantum limit on phase sensitivity, typically $\Delta\phi \sim 1/\sqrt{N}$, and push towards the Heisenberg limit $\Delta\phi \sim 1/N$. Such sensors will have applications ranging from detection of natural resources by measuring small fluctuations in local gravity, to next generation frequency and time standards, and in the search for exotic forms of dark matter with tabletop experiments. However, the majority of proposals and even experimental realizations of quantum-enhanced sensors remain at the proof-of-principle stage. This is partly due to the success which has been achieved at the single-particle level in, for example, optical lattice clocks which are comprised of a large ensemble of well-controlled alkaline earth atoms with ultra-long coherence times and which can be isolated from their environment. Even so, such systems are now reaching the point where advances based on single-particle control have diminishing returns and their sensitivity is becoming fundamentally limited by the so-called quantum noise associated with the ensemble of independent atoms. Hence, there exists a clear need to shift the paradigm towards the design and implementation of realistic protocols which use many-body effects to manipulate quantum noise and are robust to realistic sources of decohernce. In particular, the focus should be schemes which can lead to real-world applications in current and near-term state-of-the-art sensors.
Our research into this area is most broadly motivated by understanding how we can use generic many-body entanglement, beyond the typical framework of squeezed states. This combines the ability to engineer and control microscopic interactions in AMO systems with open theoretical questions, such as what are (optimal) measurements and interferometric protocols which can be implemented to utilize many-body correlations for quantum-enhanced sensing. Recent work in this direction has suggested that time-reversal schemes \cite{Davis_2016,lewis_SU11} are a promising avenue, using nonlinear dynamics to effectively amplify interferometric signals from measurements which are simple to implement, such as mean particle occupation or spin projection. Such techniques also elucidate enticing connections between quantum sensing and the study of quantum chaos and fast scrambling, as time-reversal schemes can be equivalently viewed as OTOCs. Even more intriguing is the prospect to use the core phenomena of fast scrambling, that is the rapid generation of entanglement between many-body degrees of freedom, as a guide to the design of powerful many-body states for metrology.
We explore these topics across a wide range of AMO platforms and types of sensors, with many ideas able to be transferred among different technologies. In particular, I am interested in developing sensors which use engineered interactions to couple multiple different degrees of freedom. Examples include optomechanical systems, atomic vapors, and cavity-QED and ion platforms which include coupling between spin and bosonic (motional) degrees of freedom. Here, one degree of freedom (i.e. bosonic), which is sensitive to the targeted perturbation, can be coupled to another, perhaps more controllable and observable, degree of freedom (i.e. spin) which allows an inferred measurement of the perturbation. Applications of these kind of schemes can include, e.g., tabletop sensors for detection of exotic dark matter.
Our research into this area is most broadly motivated by understanding how we can use generic many-body entanglement, beyond the typical framework of squeezed states. This combines the ability to engineer and control microscopic interactions in AMO systems with open theoretical questions, such as what are (optimal) measurements and interferometric protocols which can be implemented to utilize many-body correlations for quantum-enhanced sensing. Recent work in this direction has suggested that time-reversal schemes \cite{Davis_2016,lewis_SU11} are a promising avenue, using nonlinear dynamics to effectively amplify interferometric signals from measurements which are simple to implement, such as mean particle occupation or spin projection. Such techniques also elucidate enticing connections between quantum sensing and the study of quantum chaos and fast scrambling, as time-reversal schemes can be equivalently viewed as OTOCs. Even more intriguing is the prospect to use the core phenomena of fast scrambling, that is the rapid generation of entanglement between many-body degrees of freedom, as a guide to the design of powerful many-body states for metrology.
We explore these topics across a wide range of AMO platforms and types of sensors, with many ideas able to be transferred among different technologies. In particular, I am interested in developing sensors which use engineered interactions to couple multiple different degrees of freedom. Examples include optomechanical systems, atomic vapors, and cavity-QED and ion platforms which include coupling between spin and bosonic (motional) degrees of freedom. Here, one degree of freedom (i.e. bosonic), which is sensitive to the targeted perturbation, can be coupled to another, perhaps more controllable and observable, degree of freedom (i.e. spin) which allows an inferred measurement of the perturbation. Applications of these kind of schemes can include, e.g., tabletop sensors for detection of exotic dark matter.