arXiv subjects

R. Gautier

Publications and source records attributed to R. Gautier.

3 recordsLinked to original sources

arXiv2020

Tailoring multi-loop atom interferometers with adjustable momentum transfer

Multi-loop matter-wave interferometers are essential in quantum sensing to measure the derivatives of physical quantities in time or space. Because multi-loop interferometers require multiple reflections, imperfections of the matter-wave mirrors create spurious paths that scramble the signal of interest. Here we demonstrate a method of adjustable momentum transfer that prevents the recombination of the spurious paths in a double-loop atom interferometer aimed at measuring rotation rates. We experimentally study the recombination condition of the spurious matter waves, which is quantitatively supported by a model accounting for the coherence properties of the atomic source. We finally demonstrate the effectiveness of the method in building a cold-atom gyroscope with a single-shot acceleration sensitivity suppressed by a factor of at least 50. Our study will impact the design of multi-loop atom interferometers that measure a single inertial quantity.

physics.atom-ph↗

arXiv2020

Optimizing quantum phase estimation for the simulation of Hamiltonian eigenstates

We revisit quantum phase estimation algorithms for the purpose of obtaining the energy levels of many-body Hamiltonians and pay particular attention to the statistical analysis of their outputs. We introduce the mean phase direction of the parent distribution associated with eigenstate inputs as a new post-processing tool. By connecting it with the unknown phase, we find that if used as its direct estimator, it exceeds the accuracy of the standard majority rule using one less bit of resolution, making evident that it can also be inverted to provide unbiased estimation. Moreover, we show how to directly use this quantity to accurately find the energy levels when the initialized state is an eigenstate of the simulated propagator during the whole time evolution, which allows for shallower algorithms. We then use IBM Q hardware to carry out the digital quantum simulation of three toy models: a two-level system, a two-spin Ising model and a two-site Hubbard model at half-filling. Methodologies are provided to implement Trotterization and reduce the variability of results in noisy intermediate scale quantum computers.

quant-ph↗

arXiv2020

Accurate trajectory alignment in cold-atom interferometers with separated laser beams

Cold-atom interferometers commonly face systematic effects originating from the coupling between the trajectory of the atomic wave packet and the wave front of the laser beams driving the interferometer. Detrimental for the accuracy and the stability of such inertial sensors, these systematics are particularly enhanced in architectures based on spatially separated laser beams. Here we analyze the effect of a coupling between the relative alignment of two separated laser beams and the trajectory of the atomic wave packet in a four-light-pulse cold-atom gyroscope operated in fountain configuration. We present a method to align the two laser beams at the $0.2 \ μ$rad level and to determine the optimal mean velocity of the atomic wave packet with an accuracy of $0.2\ \textrm{mm}\cdot\textrm{s}^{-1}$. Such fine tuning constrains the associated gyroscope bias to a level of $1\times 10^{-10}~\textrm{rad}\cdot\textrm{s}^{-1}$. In addition, we reveal this coupling using the point-source interferometry technique by analyzing single-shot time-of-flight fluorescence traces, which allows us to measure large angular misalignments between the interrogation beams. The alignment method which we present here can be employed in other sensor configurations and is particularly relevant to emerging gravitational wave detector concepts based on cold-atom interferometry.

physics.atom-ph↗