arXiv subjects

S. F. Yelin

Publications and source records attributed to S. F. Yelin.

At least 19 recordsLinked to original sources

arXiv2024

Superradiance-assisted two-color Doppler cooling of molecules

For experiments that require a quantum system to be in the ultra-cold regime, laser cooling is an essential tool. While techniques for laser cooling ions and neutral atoms have been refined and temperatures below the Doppler limit have been achieved, present-day techniques are limited to a small class of molecules. This paper proposes a general cooling scheme for molecules based on vibrational-state transitions. Superradiance is used to speed up the two-photon transition. Simulations of this scheme achieve temperatures comparable to those achieved by existing two-level schemes for neutral atoms and ions.

physics.atom-ph↗

arXiv2023

A phonon laser in the quantum regime

We demonstrate a trapped-ion system with two competing dissipation channels, implemented independently on two ion species co-trapped in a Paul trap. By controlling coherent spin-oscillator couplings and optical pumping rates we explore the phase diagram of this system, which exhibits a regime analogous to that of a (phonon) laser but operates close to the quantum ground state with an average phonon number of $\bar{n}<10$. We demonstrate phase locking of the oscillator to an additional resonant drive, and also observe the phase diffusion of the resulting state under dissipation by reconstructing the quantum state from a measurement of the characteristic function.

quant-ph↗

arXiv2021

Noise-Resilient Phase Transitions and Limit-Cycles in Coupled Kerr Oscillators

Driven-dissipative quantum many-body systems have been the subject of many studies in recent years. They possess unique, novel classes of dissipation-stabilized quantum many-body phases including the limit cycle. For a long time it has been speculated if such a behavior, a recurring phenomenon in non-linear classical and quantum many-body systems, can be classified as a time crystal. However, the robustness of these periodic dynamics, against quantum fluctuations is an open question. In this work we seek the answer to this question in a canonical yet important system, i.e., a multi-mode cavity with self and cross-Kerr non-linearity, including the fluctuation effects via higher order correlations. Employing the Keldysh path integral, we investigate the Green's function and correlation of the cavity modes in different regions. Furthermore, we extend our analysis beyond the mean-field by explicitly including the effect of two-body correlations via the 2nd-cumulant expansion. Our results shed light on the emergence of dissipative phase transitions in open quantum systems and clearly indicate the robustness of limit-cycle oscillations in the presence of the quantum fluctuations.

quant-ph↗

arXiv2018

Optical Control of a Single Nuclear Spin in the Solid State

We demonstrate a novel method for coherent optical manipulation of individual nuclear spins in the solid state, mediated by the electronic states of a proximal quantum emitter. Specifically, using the nitrogen-vacancy (NV) color center in diamond, we demonstrate control of a proximal $^{14}$N nuclear spin via an all-optical Raman technique. We evaluate the extent to which the intrinsic physical properties of the NV center limit the performance of coherent control, and find that it is ultimately constrained by the relative rates of transverse hyperfine coupling and radiative decay in the NV center's excited state. Possible extensions and applications to other color centers are discussed.

quant-ph↗

arXiv2016

A novel regime for the dynamical Casimir effect

The dynamical Casimir effect (DCE) is the production of photons by the amplification of vacuum fluctuations. In this paper we demonstrate new resonance conditions in DCE that potentially allow the production of optical photons when the mechanical frequency is smaller than the lowest frequency of the cavity field. We consider a cavity with one mirror fixed and the other allowed to oscillate. In order to identify the region where production of photons takes place, we do a linear stability analysis and investigate the dynamic stability of the system under small fluctuations. By using a numerical solution of the Heisenberg equations of motion, the time evolution of the number of photons produced in the unstable region is studied.

quant-ph↗

arXiv2014

Spin Squeezing by means of Driven Superradiance

We discuss the possibility of generating spin squeezed states by means of driven superradiance, analytically affirming and broadening the finding in [Phys. Rev. Lett. 110, 080502 (2013)]. In an earlier paper [Phys. Rev. Lett. 112, 140402 (2014)] the authors determined that spontaneous purely-dissipative Dicke model superradiance failed to generate any entanglement over the course of the system's time evolution. In this article we show that by adding a driving field, however, the Dicke model system can be tuned to evolve toward an entangled steady state. We discuss how to optimize the driving frequency to maximize the entanglement. We show that the resulting entanglement is fairly strong, in that it leads to spin squeezing.

quant-ph↗

arXiv2014

Certifying Separability in Symmetric Mixed States, and Superradiance

Separability criteria are typically of the necessary, but not sufficient, variety, in that satisfying some separability criterion, such as positivity of eigenvalues under partial transpose, does not strictly imply separability. Certifying separability amounts to proving the existence of a decomposition of a target mixed state into some convex combination of separable states; determining the existence of such a decomposition is "hard." We show that it is effective to ask, instead, if the target mixed state "fits" some preconstructed separable form, in that one can generate a sufficient separability criterion relevant to all target states in some family by ensuring enough degrees of freedom in the preconstructed separable form. We demonstrate this technique by inducing a sufficient criterion for "diagonally symmetric" states of N qubits. A sufficient separability criterion opens the door to study precisely how entanglement is (not) formed; we use ours to prove that, counterintuitively, entanglement is not generated in idealized Dicke model superradiance despite its exemplification of many-body effects. We introduce a quantification of the extent to which a given preconstructed parametrization comprises the set of all separable states; for "diagonally symmetric" states our preconstruction is shown to be fully complete. This implies that our criterion is necessary in addition to sufficient, among other ramifications which we explore.

quant-ph↗

arXiv2012

Studies on Negative Refractive Index without Absorption

Which systems are ideal to obtain negative refraction with no absorption? Electromagnetically induced transparency (EIT) is a method to suppress absorption and make a material transparent to a field of a given frequency. Such a system has been discussed in [1]; however the main limitations for negative refraction introduced are the necessity of resonant electric and magnetic dipole transitions, and the necessity of very dense media. We suggest using frequency translators in a composite system that would provide negative refraction for a range of optical frequencies while attempting to overcome the limitations discussed above. In the process of using frequency translators, we also find composite systems that can be used for refractive index enhancement.

physics.optics↗

arXiv2012

New Quantum Bounds for Inequalities involving Marginal Expectations

We review, correct, and develop an algorithm which determines arbitrary Quantum Bounds, based on the seminal work of Tsirelson [Lett. Math. Phys. 4, 93 (1980)]. The potential of this algorithm is demonstrated by deriving both new number-valued Quantum Bounds, as well as identifying a new class of function-valued Quantum Bounds. Those results facilitate an 8-dimensional Volume Analysis of Quantum Mechanics which extends the work of Cabello [PRA 72 (2005)]. We contrast the Quantum Volume defined be these new bounds to that of Macroscopic Locality, defined by the inequalities corresponding to the first level of the hierarchy of Navascues et al [NJP 10 (2008)], proving our function-valued Quantum Bounds to be more complete.

quant-ph↗

arXiv2012

Cluster state generation using van der Waals and dipole-dipole interactions in optical lattices

We present a scalable method for generation of a cluster state for measurement-based quantum computing using van der Waals or dipole-dipole interactions between neutral atoms or polar molecules in an optical lattice. Nearest neighbor entanglement is accomplished by performing a phase gate using interaction of atoms in Rydberg states or molecules in large dipole moment states. All nearest neighbors are sequentially entangled in a finite number of operations, independent of the number of qubits, producing a 1D cluster state. A universal 2D cluster state can be generated in several ms in a two-dimensional optical lattice by producing a series of 1D cluster states in one lattice direction, followed by application of the entangling operations in another lattice direction. We discuss the viability of the scheme with Rb Rydberg atoms.

quant-ph↗

arXiv2011

Superradiance in spin-$J$ particles: Effects of multiple levels

We study the superradiance dynamics in a dense system of atoms each of which can be generally a spin-$j$ particle with $j$ an arbitrary half-integer. We generalize Dicke's superradiance point of view to multiple-level systems, and compare the results based on a novel approach we have developed in {[}Yelin \textit{et al.}, arXiv:quant-ph/0509184{]}. Using this formalism we derive an effective two-body description that shows cooperative and collective effects for spin-$j$ particles, taking into account the coherence of transitions between different atomic levels. We find that the superradiance, which is well-known as a many-body phenomenon, can also be modified by multiple level effects. We also discuss the feasibility and propose that our approach can be applied to polar molecules, for their vibrational states have multi-level structure which is partially harmonic.

quant-ph↗

arXiv2011

Ion crystal transducer for strong coupling between single ions and single photons

A new approach for realization of a quantum interface between single photons and single ions in an ion crystal is proposed and analyzed. In our approach the coupling between a single photon and a single ion is enhanced via the collective degrees of freedom of the ion crystal. Applications including single-photon generation, a memory for a quantum repeater, and a deterministic photon-photon, photon-phonon, or photon-ion entangler are discussed.

quant-ph↗

arXiv2009

Single photon nonlinearities using arrays of cold polar molecules

We model single photon nonlinearities resulting from the dipole-dipole interactions of cold polar molecules. We propose utilizing ``dark state polaritons'' to effectively couple photon and molecular states; through this framework, coherent control of the nonlinearity can be expressed and potentially used in an optical quantum computation architecture. Due to the dipole-dipole interaction the photons pick up a measurable nonlinear phase even in the single photon regime. A manifold of protected symmetric eigenstates is used as basis. Depending on the implementation, major sources of decoherence result from non-symmetric interactions and phonon dispersion. We discuss the strength of the nonlinearity per photon and the feasibility of this system.

quant-ph↗

arXiv2008

Electromagnetically induced spatial light modulation

We theoretically report that, utilizing electromagnetically induced transparency (EIT), the transverse spatial properties of weak probe fields can be fast modulated by using optical patterns (e.g. images) with desired intensity distributions in the coupling fields. Consequently, EIT systems can function as high-speed optically addressed spatial light modulators. To exemplify our proposal, we indicate the generation and manipulation of Laguerre-Gaussian beams based on either phase or amplitude modulation in hot vapor EIT systems.

quant-ph↗

arXiv2008

Coherent Graphene Devices: Movable Mirrors, Buffers and Memories

We theoretically report that, at a sharp electrostatic step potential in graphene, massless Dirac fermions can obtain Goos-Hänchen-like shifts under total internal reflection. Based on these results, we study the coherent propagation of the quasiparticles along a sharp graphene \emph{p-n-p} waveguide and derive novel dispersion relations for the guided modes. Consequently, coherent graphene devices (e.g. movable mirrors, buffers and memories) induced only by the electric field effect can be proposed.

cond-mat.other↗

arXiv2008

Photon generation from vacuum in non-stationary circuit QED

We study theoretically the non-stationary circuit QED system in which the artificial atom transition frequency has a small periodic modulation in time, prescribed externally. We show that, in the dispersive regime, when the modulation periodicity meets the `resonances', the dynamics may be described by the dynamical Casimir effect, Jaynes-Cummings or Anti-Jaynes-Cummings effective Hamiltonians. In the resonant atom-cavity regime, under the modulation `resonance' the dynamics resembles the behavior of the dynamical Casimir effect in a vibrating cavity containing a resonant two-level atom, and entangled states with two photons can be created from vacuum. Thus, an analog of the dynamical Casimir effect may be simulated in circuit QED, and several photons, as well as entangled states, can be generated from vacuum due to the anti-rotating term in the Rabi Hamiltonian.

quant-ph↗

arXiv2008

Formation of deeply bound molecules via chainwise adiabatic passage

We suggest and analyze a novel technique for efficient and robust creation of dense ultracold molecular ensembles in their ground rovibrational state. In our approach a molecule is brought to the ground state through a series of intermediate vibrational states via a {\em multistate chainwise Stimulated Raman Adiabatic Passage} (c-STIRAP) technique. We study the influence of the intermediate states decay on the transfer process and suggest an approach that minimizes the population of these states, resulting in a maximal transfer efficiency. As an example, we analyze the formation of $^{87}$Rb$_{2}$ starting from an initial Feshbach molecular state and taking into account major decay mechanisms due to inelastic atom-molecule and molecule-molecule collisions. Numerical analysis suggests a transfer efficiency $>$ 90%, even in the presence of strong collisional relaxation as are present in a high density atomic gas.

quant-ph↗

arXiv2007

Image Storage in Hot Vapors

We theoretically investigate image propagation and storage in hot atomic vapor. A $4f$ system is adopted for imaging and an atomic vapor cell is placed over the transform plane. The Fraunhofer diffraction pattern of an object in the object plane can thus be transformed into atomic Raman coherence according to the idea of ``light storage''. We investigate how the stored diffraction pattern evolves under diffusion. Our result indicates, under appropriate conditions, that an image can be reconstructed with high fidelity. The main reason for this procedure to work is the fact that diffusion of opposite-phase components of the diffraction pattern interfere destructively.

quant-ph↗