arXiv subjects

Eyal Buks

Publications and source records attributed to Eyal Buks.

At least 37 records · Page 2Linked to original sources

arXiv2022

Thermalization and disentanglement with a nonlinear Schrödinger equation

We study a recently proposed modified Schrödinger equation having an added nonlinear term. For the case where a stochastic term is added to the Hamiltonian, the fluctuating response is found to resemble the process of thermalization. Disentanglement induced by the added nonlinear term is explored for a system made of two coupled spins. A butterfly-like effect is found near fully entangled states of the spin-spin system. A limit cycle solution is found when one of the spins is externally driven.

quant-ph↗

arXiv2022

Low temperature spectrum of a fiber loop laser

Fiber-based multi-wavelength lasers have a variety of important applications in telecommunication and meteorology. We experimentally study a fiber loop laser with an integrated Erbium doped fiber (EDF). The output optical spectrum is measured as a function of the EDF temperature. We find that below a critical temperature of about $10\unit{% K}$ the measured optical spectrum exhibits a sequence of narrow and unequally-spaced peaks. An intriguing connection between the peaks' wavelengths and the sequence of prime numbers is discussed. An hypothesis, which attributes the comb formation to intermode coupling, is explored.

physics.optics↗

arXiv2022

Polarization-selective magneto-optical modulation

We study magneto-optical coupling in a ferrimagnetic sphere resonator made of Yttrium iron garnet. We find that the resonator can be operated in the telecom band as a polarization-selective optical modulator. Intermodulation gain can be employed in the nonlinear regime for amplification.

physics.optics↗

arXiv2022

Tunable degree of polarization in a Figure-8 fiber laser

We experimentally study a fiber loop laser in the Figure-8 configuration, and explore the dependency of the degree of polarization on controlled parameters. To account for the experimental observations, a mapping is derived to evaluate the polarization time evolution. Nonlinearity induced by Kerr effect and gain saturation gives rise to rich dynamics. We find that degree of polarization can be increased by tuning the system into a region where the mapping has a locally stable fixed point.

physics.optics↗

arXiv2021

Optical interface for a hybrid magnon-photon resonator

We study optical detection of magnetic resonance of a ferrimagnetic sphere resonator, which is strongly coupled to a microwave loop gap resonator. Optical fibers are employed for coupling the sphere resonator with light in the telecom band. We find that magnetic resonance can be optically detected in the region of anti-crossing between the loop gap and the ferrimagnetic resonances. By measuring the response time of the optical detection we rule out the possibility that microwave induced heating is responsible for the optical detectability.

physics.app-ph↗

arXiv2021

Quantum measurement with recycled photons

We study a device composed of an optical interferometer integrated with a ferri-magnetic sphere resonator (FSR). Magneto-optic coupling can be employed in such a device to manipulate entanglement between optical pulses that are injected into the interferometer and the FSR. The device is designed to allow measuring the lifetime of such macroscopic entangled states in the region where environmental decoherence is negligibly small. This is achieved by recycling the photons interacting with the FSR in order to eliminate the entanglement before a pulse exits the interferometer. The proposed experiment may provide some insight on the quantum to classical transition associated with a measurement process.

quant-ph↗

arXiv2021

The mean field approximation and disentanglement

The mean field approximation becomes applicable when entanglement is sufficiently weak. We explore a nonlinear term that can be added to the Schrödinger equation without violating unitarity of the time evolution. We find that the added term suppresses entanglement, without affecting the evolution of any product state. The dynamics generated by the modified Schrödinger equation is explored for the case of a two-spin 1/2 system. We find that for this example the added term strongly affects the dynamics when the Hartmann Hahn matching condition is nearly satisfied.

quant-ph↗

arXiv2021

Thermal instability in a ferrimagnetic resonator strongly coupled to a loop-gap microwave cavity

We study nonlinear response of a ferrimagnetic sphere resonator (FSR) strongly coupled to a microwave loop gap resonator (LGR). The measured response in the regime of weak nonlinearity allows the extraction of the FSR Kerr coefficient and its cubic damping rate. We find that there is a certain range of driving parameters in which the system exhibits instability. In that range, self-sustained modulation of the reflected power off the system is generated. The instability is attributed to absorption-induced heating of the FSR above its Curie temperature.

cond-mat.str-el↗

arXiv2021

Stability of the Grabert master equation

We study the dynamics of a quantum system having Hilbert space of finite dimension $d_{\mathrm{H}}$. Instabilities are possible provided that the master equation governing the system's dynamics contain nonlinear terms. Here we consider the nonlinear master equation derived by Grabert. The dynamics near a fixed point is analyzed by using the method of linearization, and by evaluating the eigenvalues of the Jacobian matrix. We find that all these eigenvalues are non-negative, and conclude that the fixed point is stable. This finding raises the question: under what conditions instability is possible in a quantum system having finite $d_{\mathrm{H}}$?

quant-ph↗

arXiv2021

Optically detected flip-flops between different spin ensembles in diamond

We employ the technique of optical detection of magnetic resonance to study dipolar interaction in diamond between nitrogen-vacancy color centers of different crystallographic orientations and substitutional nitrogen defects. We demonstrate optical measurements of resonant spin flips-flips (second Larmor line), and flip-flops between different spin ensembles in diamond. In addition, the strain coupling between the nitrogen-vacancy color centers and bulk acoustic modes is studied using optical detection. Our findings may help optimizing cross polarization protocols, which, in turn, may allow improving the sensitivity of diamond-based detectors.

quant-ph↗

arXiv2020

Instability in the Hartmann--Hahn double resonance

The Hartmann-Hahn technique allows sensitivity enhancement of magnetic resonance imaging and spectroscopy by coupling the spins under study to another spin species that is externally driven. Here we theoretically study the coupled spins' dynamics, and find that for a certain region of driving parameters the system becomes unstable. The required conditions for making this region of instability becoming experimentally accessible are discussed.

quant-ph↗

arXiv2020

Driving-induced resonance narrowing in a strongly coupled cavity-qubit system

We study a system consisting of a superconducting flux qubit strongly coupled to a microwave cavity. Externally applied qubit driving is employed in order to manipulate the spectrum of dressed states. We observe resonance narrowing in the region where the splitting between the two dressed fundamental resonances is tuned to zero. The narrowing in this region of overlapping resonances can be exploited for long-time storage of quantum states. In addition, we measure the response to strong cavity mode driving, and find a qualitative deviation between the experimental results and the predictions of a semiclassical model. On the other hand, good agreement is obtained using theoretical predictions obtained by numerically integrating the master equation governing the system's dynamics. The observed response demonstrates a process of a coherent cancellation of two meta-stable dressed states.

quant-ph↗

arXiv2020

Frequency mixing in a ferrimagnetic sphere resonator

Frequency mixing in ferrimagnetic resonators based on yttrium and calcium vanadium iron garnets (YIG and CVBIG) is employed for studying their nonlinear interactions. The ferrimagnetic Kittel mode is driven by applying a pump tone at a frequency close to resonance. We explore two nonlinear frequency mixing configurations. In the first one, mixing between a transverse pump tone and an added longitudinal weak signal is explored, and the experimental results are compared with the predictions of the Landau-Zener-Stuckelberg model. In the second one, intermodulation measurements are employed by mixing pump and signal tones both in the transverse direction for studying a bifurcation between a stable spiral and a stable node attractors. Our results are applicable for developing sensitive signal receivers with high gain for both the radio frequency and the microwave bands.

quant-ph↗

arXiv2020

Mode locking in an optomechanical cavity

We experimentally study a fiber-based optical ring cavity integrated with a mechanical resonator mirror and an optical amplifier. The device exhibits a variety of intriguing nonlinear effects including synchronization and self-excited oscillation. Passively generated optical pulses are observed when the frequency of the optical ring cavity is tuned very close to the mechanical frequency of the suspended mirror. The optical power at the threshold of this process of mechanical mode locking is found to be related to quantum noise of the optical amplifier.

quant-ph↗

arXiv2019

Musical tonality and synchronization

The current study is motivated by some observations of highly nonlinear dynamical effects in biological auditory systems. We examine the hypothesis that one of the underlying mechanisms responsible for the observed nonlinearity is self-excited oscillation (SEO). According to this hypothesis the detection and processing of input audio signals by biological auditory systems is performed by coupling the input signal with an internal element undergoing SEO. Under appropriate conditions such coupling may result in synchronization between the input signal and the SEO. In this paper we present some supporting evidence for this hypothesis by showing that some well-known phenomena in musical tonality can be explained by the Hopf model of SEO and the Arnold model of synchronization. Moreover, some mathematical properties of these models are employed as guidelines for the construction of some modulations that can be applied to a given musical composition. The construction of some intriguing patterns of musical harmony is demonstrated by applying these modulations to known musical pieces.

nlin.CD↗

arXiv2019

Self-excited oscillation and synchronization of an on-fiber optomechanical cavity

We study a fully on-fiber optomechanical cavity and characterize its performance as a sensor. The cavity is formed by patterning a suspended metallic mirror near the tip of an optical fiber and by introducing a static reflector inside the fiber. Optically induced self-excited oscillation (SEO) is observed above a threshold value of the injected laser power. The SEO phase can be synchronized by periodically modulating the optical power that is injected into the cavity. Noise properties of the system in the region of synchronization are investigated. Moreover, the spectrum is measured near different values of the modulation frequency, at which phase locking occurs. A universal behavior is revealed in the transition between the regions of phase locked and free running SEO.

quant-ph↗

arXiv2019

Multiphoton resonances in nitrogen-vacancy defects in diamond

Dense ensembles of nitrogen vacancy (NV) centers in diamond are of interest for various applications including magnetometry, masers, hyperpolarization and quantum memory. All of the applications above may benefit from a non-linear response of the ensemble, and hence multiphoton processes are of importance. We study an enhancement of the NV ensemble multiphoton response due to coupling to a superconducting cavity or to an ensemble of Nitrogen 14 substitutional defects (P1). In the latter case, the increased NV sensitivity allowed us to probe the P1 hyperfine splitting. As an example of an application, an increased responsivity to magnetic field is demonstrated.

quant-ph↗

arXiv2019

Optical detection of paramagnetic defects in diamond using off-resonance excitation of NV centers

In this work we use fluorescence from nitrogen-vacancy defects in diamond to detect and explore other paramagnetic defects in the diamond, such as P1 defects, which are commonly undetectable through optical detection of magnetic resonance in standard conditions. Our method does not require overlap between the defects' resonances and therefore is applicable in a wide region of magnetic fields and frequencies, as verified by excellent fit to theoretical predictions. We propose a depolarization scheme of P1 defects to account for the observed data. To verify our results, we perform cavity-based detection of magnetic resonance and find a good agreement between the measured optically induced polarization and the value obtained theoretically from rate equations. The findings in this work may open the way to detection of paramagnetic defects outside of the diamond through the photoluminesence of nitrogen-vacancy defects, which might be useful for imaging in biology.

quant-ph↗