Spin squeezing of a Bose-Einstein condensate via a quantum nondemolition measurement for quantum-enhanced atom interferometry (original) (raw)
Related papers
Atom interferometry with trapped Bose–Einstein condensates: impact of atom–atom interactions
New Journal of Physics, 2010
Interferometry with ultracold atoms promises the possibility of ultraprecise and ultrasensitive measurements in many fields of physics, and is the basis of our most precise atomic clocks. Key to a high sensitivity is the possibility to achieve long measurement times and precise readout. Ultracold atoms can be precisely manipulated at the quantum level and can be held for very long times in traps; they would therefore be an ideal setting for interferometry. In this paper, we discuss how the nonlinearities from atom-atom interactions, on the one hand, allow us to efficiently produce squeezed states for enhanced readout and, on the other hand, result in phase diffusion that limits the phase accumulation time. We find that low-dimensional geometries are favorable, with two-dimensional (2D) settings giving the smallest contribution of phase diffusion caused by atom-atom interactions. Even for time sequences generated by optimal control, the achievable minimal detectable interaction energy 1E min is of the order of 10 4 µ, where µ is the chemical potential of the Bose-Einstein condensate (BEC) in the trap. From these we have to conclude that for more precise measurements with atom interferometers, more sophisticated strategies, or turning off the interaction-induced dephasing during the phase accumulation stage, will be necessary.
Squeezed-light-enhanced atom interferometry below the standard quantum limit
Physical Review A, 2014
We investigate the prospect of enhancing the phase sensitivity of atom interferometers in the Mach-Zehnder configuration with squeezed light. Ultimately, this enhancement is achieved by transferring the quantum state of squeezed light to one or more of the atomic input beams, thereby allowing operation below the standard quantum limit. We analyze in detail three specific schemes that utilize (1) single-mode squeezed optical vacuum (i.e. low frequency squeezing), (2) two-mode squeezed optical vacuum (i.e. high frequency squeezing) transferred to both atomic inputs, and (3) two-mode squeezed optical vacuum transferred to a single atomic input. Crucially, our analysis considers incomplete quantum state transfer between the optical and atomic modes, and the effects of depleting the initially-prepared atomic source. Unsurprisingly, incomplete quantum state transfer degrades the sensitivity in all three schemes. We show that by measuring the transmitted photons and using information recycling [Phys. Rev. Lett. 110, 053002 (2013)], the degrading effects of incomplete quantum state transfer on the sensitivity can be substantially reduced. In particular, information recycling allows scheme (2) to operate at the Heisenberg limit irrespective of the quantum state transfer efficiency, even when depletion is significant.
Measurement-induced squeezing of a Bose-Einstein condensate
Physical Review A, 2002
We discuss the dynamics of a Bose-Einstein condensate during its nondestructive imaging. A generalized Lindblad superoperator in the condensate master equation is used to include the effect of the measurement. A continuous imaging with a sufficiently high laser intensity progressively drives the quantum state of the condensate into number squeezed states. Observable consequences of such a measurementinduced squeezing are discussed. 03.75.Fi, 42.50.Md Since its birth, quantum mechanics has led to an interpretational debate on the role played by the measurement process in its structure and its relationship to classical mechanics developed for macroscopic systems . This debate has been enriched by the realization of new experimental techniques spanning from quantum jumps in single ion traps to macroscopic entangled states in various quantum systems. Recently, the production of atomic Bose-Einstein condensates of dilute atomic gases has also paved the way to the study of dynamical phenomena of macroscopic quantum systems with the precision characteristic of atomic physics .
Faraday-imaging-induced squeezing of a double-well Bose-Einstein condensate
Physical Review A, 2021
We examine how non-destructive measurements generate spin squeezing in an atomic Bose-Einstein condensate confined in a double-well trap. The condensate in each well is monitored using coherent light beams in a Mach-Zehnder configuration that interacts with the atoms through a quantum nondemolition Hamiltonian. We solve the dynamics of the light-atom system using an exact wavefunction approach, in the presence of dephasing noise, which allows us to examine arbitrary interaction times and a general initial state. We find that monitoring the condensate at zero detection current and with identical coherent light beams minimizes the backaction of the measurement on the atoms. In the weak atom-light interaction regime, we find the mean spin direction is relatively unaffected, while the variance of the spins is squeezed along the axis coupled to the light. Additionally, squeezing persists in the presence of tunneling and dephasing noise.
Spin-Orbit-Coupled Interferometry with Ring-Trapped Bose-Einstein Condensates
Physical Review Letters
We propose a method of atom-interferometry using a spinor Bose-Einstein condensate (BEC) with a timevarying magnetic field acting as a coherent beam-splitter. Our protocol creates long-lived superpositional counterflow states, which are of fundamental interest and can be made sensitive to both the Sagnac effect and magnetic fields on the sub-µG scale. We split a ring-trapped condensate, initially in the m f = 0 hyperfine state, into superpositions of internal m f = ±1 states and condensate superflow, which are spin-orbit coupled. After interrogation, relative phase accumulation can be inferred from a population transfer to the m f = ±1 states. The counterflow generation protocol is adiabatically deterministic and does not rely on coupling to additional optical fields or mechanical stirring techniques. Our protocol can maximise the classical Fisher information for any rotation, magnetic field, or interrogation time, and so has the maximum sensitivity available to uncorrelated particles. Precision can increase with the interrogation time, and so is limited only by the lifetime of the condensate.
Mach-Zehnder interferometry with interacting trapped Bose-Einstein condensates
Physical Review A, 2011
We study trapped Bose-Einstein condensate interferometers in presence of interactions during the whole interferometer sequence with number squeezed input states. We find that a Mach-Zehnder (or Ramsey) interferometer can be surprisingly stable against the nonlinearity induced by inter-particle interactions. The phase sensitivity can overcome the shot noise limit and can be increased up to the Heisenberg limit provided that a Bayesian or Maximum-Likelihood phase estimation strategy is used. We finally show using optimal control theory and a realistic description of the condensate dynamics that Mach-Zehnder interferometry close to the Heisenberg limit can be achieved in state-of-the-art experiments.
Physical Review A, 2009
We propose to implement a sub-shot-noise matter-wave interferometer via the stimulated dissociation of a molecular Bose-Einstein condensate and study the collisional loss of atom-molecule coherence during its phase-acquisition time. The obtained n-atom states are two-atom ͓SU͑1,1͔͒ coherent states with number variance ⌬n ϰ n compared to ⌬n ϰ ͱ n for the spin ͓SU͑2͔͒ coherent states formed by coherent splitting of an atomic condensate. Consequently, the Lorentzian atom-molecule phase diffusion is faster than the Gaussian phase diffusion between separated atomic condensates by a ͱ n factor.
Planar quantum squeezing and atom interferometry
Physical Review A, 2011
We obtain a lower bound on the sum of two spin component variances, for any quantum eigenstate of the total spin operator. This gives for Hilbert spaces of fixed spin J a quantum uncertainty relation where one cannot measure all three spin components. The results can be used to derive entanglement criteria for multiple spins J at separated sites, and are useful to detect entanglement where the mean of the spin components at each site is zero.
Squeezed Atom Laser for Bose-Einstein Condensate with Minimal Length
International Journal of Theoretical Physics
We study a protocol for constructing a squeezed atom laser for a model originating from the generalized uncertainty principle. We show that the squeezing effects arising from such systems do not require any squeezed light as an input, but the squeezing appears automatically because of the structure of the model it owns. The output atom laser beam becomes squeezed due to the nonlinear interaction between the Bose-Einstein condensate and the deformed radiation field created due to the noncommutative structure. We analyze several standard squeezing techniques based on the analytical expressions followed by a numerical analysis for further insights.