arXiv subjects

Vitalie Eremeev

Publications and source records attributed to Vitalie Eremeev.

At least 19 recordsLinked to original sources

arXiv2026

Phase information transfer by post-selection in Spin--Mechanical assisted magnetometry

Quantum information transfer between light-matter-type systems is poised to enable important applications, while also serving as a testbed for theoretical investigation. Such systems can be realized with spins coupled to a mechanical oscillator, a platform that has been extensively studied both theoretically and experimentally. Early demonstrations of quantum information transfer have relied mostly on coherent control. However, measurement-induced backaction has emerged as a strong alternative for quantum control. In this work we use post-selection on the spin system as a selective backaction to refocus spin's phase information onto the mechanical oscillator. We identify physical resources and operating regimes that govern conditional phase transfer, including oscillator quantum coherence, the number of spins, the mechanical initial state, coupling strength, oscillator amplitude, and relaxation. We benchmark different scenarios using the variance as the figure of merit, estimated via two complementary approaches: a semiclassical variance estimator and a Pegg-Barnett quantum estimator. The Cramér-Rao bound is also computed for comparison. The analysis provides a framework for understanding phase transfer in high-dimensional hybrid quantum systems and for measurement-induced backaction used in quantum magnetometry.

quant-ph↗

arXiv2026

Squeezed Phonon Lasing via Floquet-Controlled Solid-State Defects

We propose a general Floquet-engineered scheme for squeezed phonon lasing that enables a continuous crossover from conventional phase-diffused phonon lasing to phase-locked squeezed phonon lasing. Our system consists of two pairs of periodically driven spins--a primary pair and an ancilla pair--coupled to a single mechanical mode. While the underlying mechanism applies generally to such spin-mechanical systems, we focus on a solid-state implementation based on color centers embedded in a circular hexagonal boron nitride (hBN) membrane. We show that the primary spins provide mechanical gain, whereas the ancilla pair engineer a dissipative channel for the Bogoliubov mode, thereby stabilizing robust steady-state squeezed phonon lasing. We support these findings through a comprehensive steady-state analysis of the lasing threshold, mechanical occupation, emission spectrum, and second-order correlations. Remarkably, we demonstrate that Floquet engineering intrinsically induces phase locking while enabling controllable quadrature squeezing, providing a simple and versatile route toward squeezed lasing in solid-state spin-mechanical platforms.

quant-ph↗

arXiv2026

Scalable phonon-laser arrays with self-organized synchronization

Quantum mechanical oscillators operating at frequencies up to the GHz regime have been predicted to support phonon lasing -- self-sustained coherent vibrational motion emerging when the effective gain exceeds intrinsic losses. Current phonon-laser proposals face two key limitations, namely: they lack scalability and rely on coupling all oscillators to a common field, which significantly restricts flexibility and prevents selective, on-demand phonon lasing at specific locations. Given that numerous applications and theoretical insights naturally emerge from scalable many-body systems, addressing these limitations is timely. In this Letter, we demonstrate how scalable arrays of individually addressable phonon lasers can be generated through local driving in a quantum many-body Ising-like spin chain. We rigorously establish the resonance conditions under which mechanical oscillators transition from thermal motion to sustained coherent self-oscillation. Unlike previous approaches that rely on a common coupling bus, our proposal employs purely local driving, resulting in an inherently modular and scalable architecture ideally suited for integration into large-scale quantum systems. Additionally, our approach enables on-demand lasing of individual mechanical oscillators at specific sites by simply switching the spin-mechanical coupling interaction on and off, provided specific resonance conditions are satisfied. Notably, our phonon laser array is robust against resonance mismatches and naturally exhibits both pairwise self-organized synchronization and global phase locking near resonance. Finally, we outline an experimental implementation within current experimental capabilities.

quant-ph↗

arXiv2024

A scaling law in optomechanically induced nonlinear oscillation

Stable limit cycle as a stabilized mechanical oscillation is the primary result of the dynamical evolution of an optomechanical system under sufficiently powerful pump. Because this dynamical process is highly nonlinear, it was not clear whether there exists a quantitative law to relate an evolved mechanical oscillation (the limit cycle of the dynamical process) to the given parameters of the fabricated system. Here, by means of the numerical simulations based on nonlinear dynamics, we demonstrate the existence of such quantitative relations that are generally valid to the nonlinear optomechanical processes. These quantitative relations can be summarized to a scaling law that is seemingly similar to those in phase transitions of many-body systems but has very different properties. Such a quantitative law enables one to find the more feasible system parameters for realizing the same or a similar dynamical evolution result, so it will be useful to the relevant experimental researches.

physics.optics↗

arXiv2024

Simultaneous photon and phonon lasing in a two-tone driven optomechanical system

Achieving simultaneous lasing of photons and phonons in optomechanical setups has great potential for applications in quantum information processing, high precision sensing and the design of hybrid photonic-phononic devices. Here, we explore this possibility with an optomechanical system driven by a two-tone field. Whenever the difference between the driving frequencies matches the associated mechanical frequency, the photon and phonon populations are found to achieve steady-state coherent oscillations, demonstrating a dual lasing phenomenon. Such drive-tone resonance condition can synchronize the phases of the photon and phonon fields, which facilitates a robust simultaneous lasing. Here, we provide analytical insights into the joint amplification of the optical and mechanical modes, and further confirm the dual lasing phenomenon by numerically calculating the relevant correlation functions and the power spectrum. Our setup, consisting of a single optomechanical cavity, is simpler than previous realizations of dual lasing and provides a clean picture of the underlying mechanisms. Our work thus paves the way for the development of novel strategies for the optimisation of optomechanical interactions through tailored driving schemes.

quant-ph↗

arXiv2024

Generation of phonon quantum states and quantum correlations among single photon emitters in hexagonal boron nitride

Hexagonal boron nitride exhibits two types of defects with great potential for quantum information technologies: single-photon emitters (SPEs) and one-dimensional grain boundaries hosting topologically-protected phonons, termed as {\it{topologically-protected phonon lines}} (TPL). Here, by means of a simple effective model and density functional theory calculations, we show that it is possible to use these phonons for the transmission of information. Particularly, a single SPE can be used to induce single-, two- and qubit-phonon states in the one dimensional channel, and \textit{(ii)} two distant SPEs can be coupled by the TPL that acts as a waveguide, thus exhibiting strong quantum correlations. We highlight the possibilities offered by this material-built-in nano-architecture as a phononic device for quantum information technologies.

quant-ph↗

arXiv2023

Transfer of quantum states and stationary quantum correlations in a hybrid optomechanical network

We present a systematic study on the effects of dynamical transfer and steady-state synchronization of quantum states in a hybrid optomechanical network, consisting of two cavities with atoms inside and interacting via a common moving mirror (i.e. mechanical oscillator), are studied. It is found that high fidelity transfer of Schrödinger's cat and squeezed states between the cavities modes is possible. Additionally, we show the effect of synchronization of cavity modes in a steady squeezed states at high fidelity realizable by the mechanical oscillator which intermediates the generation, transfer and stabilization of the squeezing. In this framework, we also have studied the generation and evolution of bipartite and tripartite entanglement and found its interconnection to the effects of transfer and synchronization. Particularly, when the transfer occurs at the maximal fidelity, at this instant any entanglement is almost zero, so the modes are disentangled. On the other hand, when the two bosonic modes are synchronized in a squeezed stationary state, then these modes are also entangled. The results found in this study may find their applicability in quantum information and computation technologies, as well in metrology setups, where the squeezed states are essential.

quant-ph↗

arXiv2022

Phonon trapping states as a witness for generation of phonon blockade in a hybrid micromaser system

In a hybrid micromaser system consisting of an optical cavity with a moving mirror connected to a low temperature thermal bath, we demonstrate, both analytically and numerically, that for certain interaction times between a random atomic flux and the optomechanical cavity, vacuum phonon trapping states are generated. Furthermore, under the approach of the master equation with independent phonon and photon thermal baths, we show that the trapping of the phonons and photons is achieved for the same interaction times. The results also indicate that by increasing the cavity-oscillator coupling one may generate a coherent phonon state aside from the trapping states. Within the same hybrid system, but now connected to the squeezed phonon reservoir, a phonon blockade effect can be engineered. Moreover, we identify an interconnection between the trapping and blockade effects, particularly if one approaches the vacuum trapping state, strong phonon blockade can be achieved when the system is connected with a weakly squeezed phonon reservoir.

quant-ph↗

arXiv2021

High-temperature phonon-mediated superconductivity in monolayer Mg2B4C2

A new two-dimensional material { Mg2B4C2, belonging to the family of the conventional superconductor MgB2, is theoretically predicted to exhibit superconductivity with critical temperature Tc estimated in the 47-48 K range (predicted using the McMillian-Allen-Dynes formula) without any tuning of external parameters such as doping, strain, or substrate-induced effects. The origin of such a high intrinsic Tc is ascribed to the presence of strong electron-phonon coupling and topological Dirac states (which are absent in MgB2) yielding a large density of states at the Fermi level. This material also features a nontrivial electronic band topology exhibiting Dirac points, practically gapless Dirac nodal lines, and topological nontrivial edge states. Consequently, it is a potential candidate for realization of topological superconductivity in 2D. This system is obtained after replacing the chemically active boron layers in MgB2 by chemically inactive boron-carbon layers. Hence, the surfaces of this material are inert. Our calculations confirm the stability of 2D Mg2B4C2. We also find that the key features of this material remain essentially unchanged when its thickness is increased by modestly increasing the number of inner MgB2 layers.

cond-mat.supr-con↗

arXiv2021

Steady-state squeezing transfer in hybrid optomechanics

A hybrid scheme is presented that allows the transfer of squeezed states (TSS) from the mechanical part to an optical cavity in the steady-state. In a standard optomechanical scheme, a three-level atom acts as an intermediate element for TSS. Two different procedures are developed that allow the visualization of the TSS effect: In the first one, we apply a coherent pump of squeezed phonons in our hybrid system, and the second method is achieved by placing the system in contact with a phonon squeezed bath. Our model and procedures show that in optomechanical systems TSS can be achieved with a high fidelity.

quant-ph↗

arXiv2020

Phonon maser stimulated by spin post-selection

In a sequence of single spins interacting longitudinally with a mechanical oscillator, and using the micromaser model with random injection, we show that after an appropriate post-selection of each spin, a phonon laser analog with Poisson statistics is created with nearly perfect coherence, evidenced by the second order coherence function that goes asymptotically to one. The non-linear gain of the system depends crucially on the properly post-selected spin state as well as the pump. Our model and results suggest that the mechanism of interaction followed by a post-selected state or partial trace (common in laser/maser theory) of the spins may create the coherent vibrational radiation. However, for situations where the mechanical losses are high and it is imposible to decrease these, then the heralded post-selection can be the only resource to get phonon lasing if compared to the partial trace operation. These ideas and results may be useful for further theoretical and technical developments.

quant-ph↗

arXiv2018

Ground-state cooling of a nanomechanical oscillator with N spins

Typical of modern quantum technologies employing nanomechanical oscillators is to demand few mechanical quantum excitations, for instance, to prolong coherence times of a particular task or, to engineer a specific non-classical state. For this reason, we devoted the present work to exhibit how to bring an initial thermalized nanomechanical oscillator near to its ground state. Particularly, we focus on extending the novel results of D. D. B. Rao \textit{et al.}, Phys. Rev. Lett. \textbf{117}, 077203 (2016), where a mechanical object can be heated up, squeezed, or cooled down near to its ground state through conditioned single-spin measurements. In our work, we study a similar iterative spin-mechanical system when $N$ spins interact with the mechanical oscillator. Here, we have also found that the postselection procedure acts as a discarding process, i.e., we steer the mechanics to the ground state by dynamically filtering its vibrational modes. We show that when considering symmetric collective spin postselection, the inclusion of $N$ spins into the quantum dynamics results highly beneficial. In particular, decreasing the total number of iterations to achieve the ground-state, with a success rate of probability comparable with the one obtained from the single-spin case.

quant-ph↗

arXiv2017

Macroscopic non-classical state preparation via post-selection

Macroscopic mechanical qubits are fundamental both to test the classical-quantum boundary and present suitable candidates for quantum information processing. Motivated by these, we propose a feasible probabilistic scheme to generate an on-demand mechanical qubit, as well as Schrödinger's cat and Fock number states. In order to accomplish this proposal, we study an open dispersive spin-mechanical system in the absence of any external driving. The procedure is solely based on spin post-selection in the weak coupling regime. Through this scheme we demonstrate that the achieved superposition is closely related to the amplification of the mean values of the mechanical quadratures as they are associated to the maximum quantum coherence.

quant-ph↗

arXiv2016

Generation and protection of Maximally Entangled State between many modes in an optical network with dissipation

We present a three-cavity network model with two modes in each cavity and a non-linear medium that generates a Kerr type interaction via both self-phase and cross-phase modulation processes. We have two main goals. The first one is to generate a multipartite Maximally Entangled State (MES), starting from the ground state of the system. We address the problem both without and with dissipation. Secondly, we want to protect the MES from decoherence. While studying the MES, we analyze different bipartite and multipartite entanglement measures. We also study the effect of an Avoided Level Crossing (ALC) identified by the critical behavior of the entanglement measures, thus showing that the quantum correlations act as a witness for such phenomena. Our findings provide the quantum tools to perform the operation of generation and protection of a maximally entangled state in a cavity QED environment.

quant-ph↗

arXiv2016

The power of a control qubit in weak measurements

In the late 80s, a curious effect suggested by Aharanov, Albert and Vaidman opened up new vistas regarding quantum measurements on weakly coupled systems. There, a combination of a "weak" finite interaction together with a "strong" post-selection measurement leads to an anomalous effect, namely the mean value of a spin-1/2 particle in the $z-$direction lies outside the conventional spectrum of $\pm$1. In this paper, we investigate the quantum control of the weak value amplification of a qubit system coupled to a meter, via a second non-interacting qubit, initially quantum correlated with the first one. Our results show that for weak measurements, the control can be remotely realized via the post-selected state of the second qubit or the degree of squeezing of the meter. Additionally, in a step towards the study of the quantum control of the amplification, we can easily manipulate the degree of quantum correlations between the initial correlated qubits. We find that the degree of Entanglement has no effect on the quantum control of the amplification. However, we have found a clear connection between the amplification and quantum discord like measurements as well as classical correlations between the qubits. Moreover, we generalize the analysis to two control qubits and we can conclude that the single control qubit scheme is more efficient. Lastly, we suggest an original application of the amplification control protocol on the enhancement of the quantum measurement accuracy, e.g. measuring the relative phase of the post-selected control qubit in a more precise way, as opposed to the no-amplification case

quant-ph↗

arXiv2014

Selftrapping triggered by losses in cavity QED

In a coupled cavity QED network model, we study the transition from a localized super fluid like state to a delocalized Mott insulator like state, triggered by losses. Without cavity losses, the transition never takes place. Further, if one measures the quantum correlations between the polaritons via the negativity, we find a critical cavity damping constant, above which the negativity displays a single peak in the same time region where the transition takes place. Additionally, we identify two regions in the parameter space, where below the critical damping, oscillations of the initial localized state are observed along with a multipeaked negativity, while above the critical value, the oscillations die out and the transition is witnessed by a neat single peaked negativity.

quant-ph↗

arXiv2014

Quantum Correlations in Cavity QED Networks

We present a Review of the dynamical features such as generation, propagation, distribution, sudden transition and freezing of the various quantum correlation measures, as Concurrence, Entanglement of Formation, Quantum Discord, as well their geometrical measure counterparts within the models of Cavity Quantum Electrodynamics Networks. Dissipation and thermal effects are discussed both in the generation of quantum correlations as well as their effect on the sudden changes and freezing of the classical and quantum correlations in a cavity quantum electrodynamical network. For certain initial conditions, double transitions in the Bures geometrical discord are found. One of these transitions tends to disappear at a critical temperature

quant-ph↗

arXiv2014

Thermal effects on the sudden changes and freezing of correlations between remote atoms in cavity QED network

We investigate the thermal effects on the sudden changes and freezing of the quantum and classical correlations of remote qubits in a cavity quantum electrodynamics (CQED) network with losses. We find that the detrimental effect of the thermal reservoirs on the system can be compensated via an efficient coupling of the fiber connecting the two cavities of the system. Furthermore, for certain initial conditions, we find a double sudden transitions in the dynamics of Bures geometrical quantum discord. The second transition tends to disappear at a critical temperature, hence freezing the discord. Finally, we discuss some ideas of the experimental realization of the present proposal.

quant-ph↗