arXiv subjects

Mark Dikopoltsev

Publications and source records attributed to Mark Dikopoltsev.

5 recordsLinked to original sources

arXiv2024

Faraday-Ramsey rotation measurement in a thin cell as an analogy to an atomic beam

Atomic beams are powerful tools for measuring spin coherence in hot vapors but require bulky setups, limiting device miniaturization. We demonstrate that micron-thin vapor cells can mimic atomic beam behavior by exploiting geometry-dependent velocity filtering. In a 5 {\mu}m rubidium cell, coherence is preserved for atoms moving parallel to the cell walls, enabling observation of the Faraday-Ramsey effect without buffer gas or anti-relaxation coatings. Using a spatially displaced pump-probe scheme and magnetic field scanning, we achieve clear Ramsey fringes and validate our model experimentally. This technique offers a compact alternative to atomic beam systems, supporting scalable sensors and frequency standards.

quant-ph↗

arXiv2022

Magnetic-field-independent spin-exchange relaxation-free magnetometer

SERF magnetometers based on dense ensembles of alkali-metal spins are precision quantum sensors that hold the record of measured and projected sensitivity to magnetic fields, in the $\mu\textrm{G}-\textrm{mG}$ range. At geomagnetic fields however, these sensors quickly lose their magnetic sensitivity due to spin decoherence by random spin-exchange collisions. Here we discover that atoms with nuclear spin $I=1/2$ can operate in the Spin-Exchange Relaxation Free (SERF) regime even at high magnetic field. We counter-intuitively show that frequent collisions between a dense and optically-inaccessible $(I=1/2)$ gas with another optically-accessible spin gas ($I>1/2$) improve the fundamental magnetic sensitivity of the latter. We analyze the performance of a dual-specie potassium and atomic hydrogen magnetometer, and project a fundamental sensitivity of about $10\,\mathrm{aT}\sqrt{\mathrm{cm}^3/\mathrm{Hz}}$ at geomagnetic fields for feasible experimental conditions.

quant-ph↗

arXiv2022

Optical protection of alkali-metal atoms from spin relaxation

We present an optical technique for suppressing relaxation in alkali-metal spins using a single off-resonant laser beam. The method harnesses a physical mechanism that synchronizes Larmor precession in the two hyperfine manifolds, protecting magnetic coherence from relaxation caused by spin-exchange and other hyperfine-changing collisions. We experimentally demonstrate up to a ninefold reduction in decoherence of warm cesium vapor, achieving simultaneous protection from both spin-exchange relaxation and partial depolarization from coated cell walls. The technique substantially enhances the spin precession quality factor and maintains a stable gyromagnetic ratio independent of spin polarization, even under frequent collisions. These findings offer a pathway for mitigating dominant relaxation channels in alkali-metal-based applications and experiments, particularly in anti-relaxation-coated cells.

quant-ph↗

arXiv2022

Suppressing the Decoherence of Alkali-Metal Spins at Low Magnetic Fields

Interactions of electron spins with rotational degrees of freedom during collisions or with external fields are fundamental processes that limit the coherence time of spin gases. We experimentally study the decoherence of hot cesium spins dominated by spin rotation-interaction during binary collisions with N$_2$ molecules or by absorption of near-resonant light. We report an order of magnitude suppression of the spin decoherence rate by either of those processes at low magnetic fields. This work extends the use of magnetic fields as a control knob, not only to suppress decoherence from random spin-conserving processes in the Spin-Exchange Relaxation Free (SERF) regime but also to suppress processes that relax electron spins rather than conserve them.

quant-ph↗

arXiv2013

Nonlinear Elimination of Spin-Exchange Relaxation of High Magnetic Moments

Relaxation of the Larmor magnetic moment by spin-exchange collisions has been shown to diminish for high alkali densities, resulting from the linear part of the collisional interaction. In contrast, we demonstrate both experimentally and theoretically the elimination of spin-exchange relaxation of high magnetic moments (birefringence) in alkali vapor. This elimination originates from the nonlinear part of the spin-exchange interaction, as a scattering process of the Larmor magnetic moment. We find counter-intuitively that the threshold magnetic field is the same as in the Larmor case, despite the fact that the precession frequency is twice as large.

quant-ph↗