Thesis Dissertation Defense

Abstract: An important frontier of research in metrology is the development of techniques to surpass the standard quantum limit using quantum squeezed states or other entangled states. In this talk, we report the first observation of squeezed ground states generation in an 87Rb spinor condensate [1]. The measurement of squeezed ground states builds on previous experiments of spin-nematic squeezing [2]. A spin-1 Bose-Einstein condensate is tuned near the quantum critical point between the polar and ferromagnetic quantum phases to create a ground state with squeezing properties. In contrast to typical non-equilibrium methods for preparing atomic squeezed states by quenching through a quantum phase transition [2], squeezed ground states are time-stationary and remain squeezed for the lifetime of the condensate. A squeezed ground state with a metrological improvement up to 6 − 8 dB and a constant squeezing angle maintained over 2 s is demonstrated.

A protocol consisting of a pair of controlled quenches of an external magnetic field is applied, which allows fast tuning of the system Hamiltonian in the vicinity of a phase transition [3]. Our protocol effectively shortcuts the adiabatic technique, overcoming the challenge of maintaining adiabaticity in the neighborhood of the quantum critical point where the frequency scale of the final Hamiltonian evolution tends to zero. This protocol is indicative of creating eigenstates of the system through the non-adiabatic method and lay the foundation for future experiments involving entangled eigenstates generation.

Reference:

[1] L. Xin, M. Barrios, J. T. Cohen, and M. S. Chapman, “Squeezed ground states in a spin-1 bose-einstein condensate,” arXiv.2202.12338, 2022.

[2] C. D. Hamley, C. S. Gerving, T. M. Hoang, E. M. Bookjans, and M. S. Chapman. Spin-nematic squeezed vacuum in a quantum gas. Nature Physics, 8(4):305–308, 2012.

[3] L. Xin, M. S. Chapman, and T. A. B. Kennedy, “Fast generation of time-stationary spin-1 squeezed states by nonadiabatic control,” PRX Quantum, vol. 3, p. 010 328, 1 Feb. 2022.