arXiv subjects

F. Martin Ciurana

Publications and source records attributed to F. Martin Ciurana.

6 recordsLinked to original sources

arXiv2017

Entanglement-enhanced phase estimation without prior phase information

We study the generation of planar quantum squeezed (PQS) states by quantum non-demolition (QND) measurement of a cold ensemble of $^{87}$Rb atoms. Precise calibration of the QND measurement allows us to infer the conditional covariance matrix describing the $F_y$ and $F_z$ components of the PQS, revealing the dual squeezing characteristic of PQS. PQS states have been proposed for single-shot phase estimation without prior knowledge of the likely values of the phase. We show that for an arbitrary phase, the generated PQS gives a metrological advantage of at least 3.1 dB relative to classical states. The PQS also beats traditional squeezed states generated with the same QND resources, except for a narrow range of phase values. Using spin squeezing inequalities, we show that spin-spin entanglement is responsible for the metrological advantage.

quant-ph↗

arXiv2017

Entanglement-enhanced radio-frequency field detection and waveform sensing

We demonstrate a new technique for detecting components of arbitrarily-shaped radio-frequency waveforms based on stroboscopic back-action evading measurements. We combine quantum non-demolition measurements and stroboscopic probing to detect waveform components with magnetic sensitivity beyond the standard quantum limit. Using an ensemble of $1.5\times 10^6$ cold rubidium atoms, we demonstrate entanglement-enhanced sensing of sinusoidal and linearly chirped waveforms, with 1.0(2)dB and 0.8(3)dB metrologically relevant noise reduction, respectively. We achieve volume-adjusted sensitivity of $δ\rm{B}\sqrt{V}\approx 11.20~\rm{fT\sqrt{cm^3/Hz}}$, comparable to the best RF~magnetometers.

physics.atom-ph↗

arXiv2016

Real-time shot-noise-limited differential photodetection for atomic quantum control

We demonstrate high-efficiency, shot-noise-limited differential photodetection with real-time signal conditioning, suitable for feedback-based quantum control of atomic systems. The detector system has quantum efficiency of 0.92, is shot-noise limited from 7.4 x 10^5 to 3.7 x 10^8 photons per pulse, and provides real-time voltage-encoded output at up to 2.3 Mpulses per second.

physics.optics↗

arXiv2014

Generation of macroscopic singlet states in a cold atomic ensemble

We report the generation of a macroscopic singlet state in a cold atomic sample via quantum non-demolition (QND) measurement induced spin squeezing. We observe 3 dB of spin squeezing and detect entanglement of up to $5.5\times10^5 $ atoms with $5σ$ statistical significance using a generalized spin squeezing inequality. The degree of squeezing implies at least 50% of the atoms have formed singlets, while the response to a magnetic field gradient indicates entanglement bonds at all length scales, a characteristic of quantum spin liquids.

quant-ph↗

arXiv2014

Ultrasensitive Atomic Spin Measurements with a Nonlinear Interferometer

We study nonlinear interferometry applied to a measurement of atomic spin and demonstrate a sensitivity that cannot be achieved by any linear-optical measurement with the same experimental resources. We use alignment-to-orientation conversion, a nonlinear-optical technique from optical magnetometry, to perform a nondestructive measurement of the spin alignment of a cold $^{87}$Rb atomic ensemble. We observe state-of-the-art spin sensitivity in a single-pass measurement, in good agreement with covariance-matrix theory. Taking the degree of measurement-induced spin squeezing as a figure of merit, we find that the nonlinear technique's experimental performance surpasses the theoretical performance of any linear-optical measurement on the same system, including optimization of probe strength and tuning. The results confirm the central prediction of nonlinear metrology, that superior scaling can lead to superior absolute sensitivity.

quant-ph↗

arXiv2013

Feedback-cooling of an atomic spin ensemble

We describe a measurement-and-feedback technique to deterministically prepare low-entropy states of atomic spin ensembles. Using quantum non-demolition measurement and incoherent optical feedback, we drive arbitrary states in the spin-orientation space toward the origin of the spin space. We observe 12 dB of spin noise reduction, or a factor of 63 reduction in phase-space volume. We find optimal feedback conditions and show that multi-stage feedback is advantageous. An input-output calculation of quantum noise incorporating realistic quantum noise sources and experimental limitations agrees well with the observations. The method may have application to generation of exotic phases of ultracold gases, for example macroscopic singlet states and valence-bond solids.

quant-ph↗