Spinor Bose-Einstein Condensate Research Articles

Spin-driven stationary turbulence in spinor Bose-Einstein condensates

Spin-driven stationary turbulence in spinor Bose-Einstein condensates

Quantum phases in spin-orbit-coupled Floquet spinor Bose gases

We propose a spin-orbit-coupled Floquet spinor Bose-Einstein condensate (BEC) which can be implemented by Floquet engineering of a quadratic Zeeman field. The Floquet spinor BEC has a Bessel-function-modulated Rabi frequency and a Floquet-induced spin-exchange interaction. The quantum phase diagram of the spin-orbit-coupled Floquet spinor BEC is investigated by considering antiferromagnetic or ferromagnetic spin-spin interactions. In comparison with the usual spin-orbit-coupled spin-1 BEC, we find that a stripe phase for antiferromagnetic interactions can exist in a large quadratic Zeeman field regime, and a different stripe phase with an experimentally favorable contrast for ferromagnetic interactions is uncovered.

Soliton collisions in spin–orbit coupled spin-1 Bose–Einstein condensates

We investigate analytically the effects of spin–orbit coupling (SOC) for the dynamics of soliton collisions in spin-1 Bose–Einstein condensates (BECs). Applying the non-standard Hirota’s bilinear method, we derive some exact one- and two-soliton solutions for the one-dimensional system of a spin–orbit coupled spin-1 BEC, which clearly shows how the dynamics of the solitons in spinor BECs can be engineered by SOC. Under SOC, the soliton collisions of ferromagnetic-polar type, ferromagnetic-ferromagnetic type and polar-polar type are discussed in details. Comparisons for the soliton states between the systems with and without SOC are displayed, a remarkable phenomenon is that the SOC can lead to the split of a soliton.

O(1) benchmarking of precise rotation in a spin-squeezed Bose-Einstein condensate

Benchmarking a high-precision quantum operation is a big challenge for many quantum systems in the presence of various noises as well as control errors. Here we propose an $O(1)$ benchmarking of a dynamically corrected rotation by taking quantum advantage of a squeezed spin state in a spin-1 Bose-Einstein condensate (BEC). Our analytical and numerical results show that tiny rotation infidelity, defined by $1\ensuremath{-}F$ with $F$ the rotation fidelity, can be calibrated in the order of $1/{N}^{2}$ by only several measurements of the rotation error for $N$ atoms in an optimally squeezed spin state. Such an $O(1)$ benchmarking is possible not only in a spin-1 BEC but also in other many-spin or many-qubit systems if a squeezed or entangled state is available.

Dynamical mean-field-driven spinor-condensate physics beyond the single-mode approximation

$^{23}\mathrm{Na}$ spin-1 Bose-Einstein condensates are used to experimentally demonstrate that mean-field physics beyond the single-mode approximation can be relevant during the nonequilibrium dynamics. The experimentally observed spin oscillation dynamics and associated dynamical spatial structure formation confirm theoretical predictions that are derived by solving a set of coupled mean-field Gross-Pitaevskii equations [J. Jie et al., Phys. Rev. A 102, 023324 (2020)]. The experiments rely on microwave dressing of the $f=1$ hyperfine states, where $f$ denotes the total angular momentum of the $^{23}\mathrm{Na}$ atom. The fact that physics beyond the single-mode approximation at the mean-field level, i.e., spatial mean-field dynamics that distinguishes the spatial density profiles associated with different Zeeman levels, can, in certain parameter regimes, have a pronounced effect on the dynamics when the spin healing length is comparable to or larger than the size of the Bose-Einstein condensate has implications for using Bose-Einstein condensates as models for quantum phase transitions and spin squeezing studies as well as for nonlinear SU(1,1) interferometers.

Hybrid approximation approach to the generation of atomic squeezing with quantum nondemolition measurements

We analyze a scheme that uses quantum nondemolition measurements to induce squeezing of a spinor Bose-Einstein condensate in a double well trap. In a previous paper [Ilo-Okeke et al. Phys. Rev. A \textbf{104}, 053324 (2021)], we introduced a model to solve exactly the wavefunction for all atom-light interaction times. Here, we perform approximations for the short interaction time regime, which is relevant for producing squeezing. Our approach uses a Holstein-Primakoff approximation for the atoms while we treat the light variables exactly. It allows us to show that the measurement induces correlations within the condensate, which manifest in the state of the condensate as a superposition of even parity states. In the long interaction time regime, our methods allow us to identify the mechanism for loss of correlation. We derive simple expressions for the variances of atomic spin variables conditioned on the measurement outcome. We find that the results agree with the exact solution in the short interaction time regime. Additionally, we show that the expressions are the sum of the variances of the atoms and the measurement. Beyond the short interaction time regime, our scheme agrees qualitatively with the exact solution for the spin variable that couples to light.

Nonlinear modes coupling of trapped spin–orbit coupled spin-1 Bose–Einstein condensates

We study analytically and numerically the nonlinear collective dynamics of quasi-one-dimensional spin–orbit coupled spin-1 Bose–Einstein condensates trapped in harmonic potential. The ground state of the system is determined by minimizing the Lagrange density, and the coupled equations of motions for the center-of-mass coordinate of the condensate and its width are derived. Then, two low energy excitation modes in breathing dynamics and dipole dynamics are obtained analytically, and the mechanism of exciting the anharmonic collective dynamics is revealed explicitly. The coupling among spin–orbit coupling, Raman coupling and spin-dependent interaction results in multiple external collective modes, which leads to the anharmonic collective dynamics. The cooperative effect of spin momentum locking and spin-dependent interaction results in coupling of dipolar and breathing dynamics, which strongly depends on spin-dependent interaction and behaves distinct characters in different phases. Interestingly, in the absence of spin-dependent interaction, the breathing dynamics is decoupled from spin dynamics and the breathing dynamics is harmonic. Our results provide theoretical evidence for deep understanding of the ground sate phase transition and the nonlinear collective dynamics of the system.

Seeded spin-mixing interferometry with long-time evolution in microwave-dressed sodium spinor Bose-Einstein condensates

We experimentally demonstrate a new type of spin-mixing interferometry in sodium Bose–Einstein condensates (BECs) based on seeded initial states. Seeding is useful because it speeds up the generation of entangled pairs, allowing many collisions to take place quickly, creating large populations in the arms of the interferometer. The entangled probe states of our interferometer are generated via spin-exchange collisions in F = 1 spinor BECs, where pairs of atoms with the magnetic quantum number collide and change into pairs with . Our results show that our seeded spin-mixing interferometer beats the standard quantum limit (SQL) with a metrological gain of 3.69 dB with spin-mixing time t = 10 ms in the case of single-sided seeding, and 3.33 dB with spin-mixing time t = 8 ms in the case of double sided seeding. The mechanism for beating the SQL is two-mode spin squeezing generated via spin-exchange collisions. Our results on spin-mixing interferometry with seeded states are useful for future quantum technologies such as quantum-enhanced microwave sensors, and quantum parametric amplifiers based on spin-mixing.

Magnetized and unmagnetized phases of trapped spin-orbit coupled spin-1 Bose-Einstein condensates

We study the ground state phases of quasi-one-dimensional spin-orbit coupled spin-1 Bose-Einstein condensates trapped in harmonic potential. Based on variational analysis, the conditions of phase transition between magnetized and unmagnetized phases are obtained analytically for the first time, and the physical mechanism of inducing phase transition is revealed. The competition relationship among spin-independent interaction, spin-dependent interaction, spin-orbit (SO) coupling and harmonic potential for generating phase transition is discussed systematically. We predict that the spin-dependent interaction plays key role in ground state phase transition. Interestingly, the phase transition of the ground state degenerate to the single particle case in free space when spin-dependent interaction is absent. In addition, the harmonic potential strengthens the influence of atomic interactions on the phase boundary. Our results provide theoretical evidence for deep understanding the ground sate phase transition of the system.

Dynamics of spin-nematic bright solitary waves in spin-tensor-momentum coupled Bose-Einstein condensates

We explore the dynamics of bright solitary waves in one-dimensional spin-tensor-momentum coupled spin-1 Bose-Einstein condensates. Our results show that the solitary waves have nonzero spin and nematicity simultaneously, hence we call them spin-nematic solitary waves. The ground-state solitary waves carry a finite momentum and display the zero-energy modes arising from symmetry breaking. In the motion of the solitary wave, the spin-tensor-momentum coupling induces the flip of the spin-nematic vector on a unit Bloch sphere, which in turn produces a force to result in the oscillatory motion of the solitary wave. The effects of a harmonic trap are also analyzed. These findings reveal the unique properties of solitary waves affected by the spin-tensor-momentum coupling.

Excited-state quantum phase transitions and Loschmidt-echo spectra in a spinor Bose-Einstein condensate

Identifying dynamical signatures of excited-state quantum phase transitions (ESQPTs) in experimentally realizable quantum many-body systems is helpful for understanding the dynamical effects of ESQPTs. In such systems, the highly controllable spinor Bose-Einstein condensates (BECs) offer an exceptional platform to study ESQPTs. In this work, we investigate the dynamical characteristics of the ESQPT in spin-1 BEC by means of the Loschmidt echo spectrum. The Loschmidt echo spectrum is an extension of the well-known Loschmidt echo and defined as the overlaps between the evolved state and the excited states of the initial Hamiltonian. We show that both the time-evolved and long-time-averaged Loschmidt echo spectrum undergo a remarkable change as the system passes through the critical point of the ESQPT. Moreover, the particular behavior exhibited by the Loschmidt echo spectrum at the critical point stands as a dynamical detector for probing the ESQPT. We further demonstrate how to capture the features of the ESQPT by using the energy distribution associated with the Loschmidt echo spectrum for time-evolved and long-time-averaged cases, respectively. Our findings contribute to a further verification of the usefulness of the Loschmidt echo spectrum for witnessing various quantum phase transitions in many-body systems and provide a different way to experimentally examine the dynamical consequences of ESQPTs.

Nonautonomous Breather and Rogue Wave in Spinor Bose–Einstein Condensates with Space-Time Modulated Potentials

To study controlled evolution of nonautonomous matter-wave breathers and rogue waves in spinor Bose–Einstein condensates with spatiotemporal modulation, we focus on a system of three coupled Gross–Pitaevskii equations with spacetime-dependent external potentials and temporally modulated gain-loss distributions. With different external potentials and gain-loss distributions, various solutions for controlled nonautonomous matter-wave breathers and rogue waves are derived by the Darboux transformation method, such as breathers and rogue waves on arched and constant backgrounds which have the periodic and parabolic trajectories. Effects of the gain-loss distribution and linear potential on the breathers and rogue waves are studied. Nonautonomous two-breathers on the arched and constant backgrounds are also derived.

Bright matter-wave bound soliton molecules in spin-1 Bose–Einstein condensates with non-autonomous nonlinearities

This work deals with matter-wave bright soliton molecules in spin-1 Bose–Einstein condensates described by three-component Gross–Pitaevskii equations with non-autonomous nonlinearities that can be tuned by Feshbach resonance management. Notably, it portrays the possibility to generate bright bound soliton molecules with the help of an exact analytic solution under a controlled velocity resonance mechanism. Results show that these soliton molecules experience the effects of time-varying nonlinearities and modulate themselves during propagation by keeping their stable properties. Significantly, the chosen periodic and kink-like nonlinearities expose the snaking, bending, compression, and amplification of multi-structured soliton molecules along with appreciable changes in their amplitude, velocity, width, and oscillations of the molecule profiles. The present results will add significant knowledge to a complete understanding beyond the known interaction dynamics of matter-wave bright solitons in spinor condensates.

Multi-solitons in the spin-orbit-coupled spin-1 Bose-Einstein condensates

We find a restrictive integrable reduction for the one-dimensional spin-orbit-coupled spin-1 Bose-Einstein condensate system, which allows us to reduce the three-component Gross-Pitaevskii system into the two-component Manakov system or the single cubic Schrödinger equation. Based on the reduction, we obtain the multi-breathers, higher-order rouge waves and multi-dark soliton solutions for ferromagnetic and anti-ferromagnetic system, respectively. Furthermore, the impacts of the spin-orbit coupling to the multi-soliton dynamics, and the stability of these soliton solutions have also been discussed.

Spin-orbit-coupled spinor gap solitons in Bose-Einstein condensates

Spin-1 spin-orbit-coupled spinor Bose-Einstein condensates have been realized in experiment. We study spin-orbit-coupled spinor gap solitons in this experimentally realizable system with an optical lattice. The spin-dependent parity symmetry of the spin-orbit coupling plays an important role in properties of gap solitons. Two families of solitons with opposite spin-dependent parity are found. Using an approximating model by replacing the optical lattice with a Harmonic trap, we demonstrate the physical origination of these two families. For a large negative quadratic Zeeman shift, we also find a type of gap solitons that spontaneously breaks the spin-dependent parity symmetry due to the ferromagnetic spinor interactions.

Controlled nonautonomous matter–wave solitons in spinor Bose–Einstein condensates with spatiotemporal modulation

To study controlled evolution of nonautonomous matter–wave solitons in spinor Bose–Einstein condensates with spatiotemporal modulation, we focus on a system of three coupled Gross–Pitaevskii (GP) equations with space–time-dependent external potentials and temporally modulated gain/loss distributions. An integrability condition and a nonisospectral Lax pair for the coupled GP equations are obtained. Using it, we derive an infinite set of dynamical invariants, the first two of which are the mass and momentum. The Darboux transform is used to generate one- and two-soliton solutions. Under the action of different external potentials and gain/loss distributions, various solutions for controlled nonautonomous matter–wave solitons of both ferromagnetic and polar types are obtained, such as self-compressed, snake-like and stepwise solitons, and as well as breathers. In particular, the formation of states resembling rogue waves, under the action of a sign-reversible gain–loss distribution, is demonstrated too. Shape-preserving and changing interactions between two nonautonomous matter–wave solitons and bound states of solitons are addressed too. In this context, spin switching arises in the polar-ferromagnetic interaction. Stability of the nonautonomous matter–wave solitons is verified by means of systematic simulations of their perturbed evolution.

Vector peregrine composites on the periodic background in spin–orbit coupled Spin-1 Bose–Einstein condensates

Vector Gross–Pitaevskii system in spin–orbit coupled Spin-1 Bose–Einstein condensates is simplified into Manakov system. By means of the nonrecursive Darboux method, vector Peregrine solutions were given, including first-order and second-order vector Peregrine solutions with four structural parameters. From these solutions, vector peregrine composites on the periodic background are found by modulating the magnitudes of four structural parameters, including first-order and second-order Peregrine structures on the periodic background, and Peregrine doublets and Peregrine “three sisters” on the periodic background. The influence of the wave number and amplitude parameters on the first-order and second-order Peregrine structures on the periodic background for three components is studied. These results will provide a deeper understanding of nonlinear wave phenomena in spin–orbit coupled Spin-1 Bose–Einstein condensates.

Dynamical quantum phase transitions in a spinor Bose-Einstein condensate and criticality enhanced quantum sensing

Quantum phase transitions universally exist in the ground and excited states of quantum many-body systems, and they have a close relationship with the nonequilibrium dynamical phase transitions, which however are challenging to identify. In the system of spin-1 Bose-Einstein condensates, though dynamical phase transitions with correspondence to equilibrium phase transitions in the ground state and uppermost excited state have been probed, those taking place in intermediate excited states remain untouched in experiments thus far. Here we unravel that both the ground- and excited-state quantum phase transitions in spinor condensates can be diagnosed with dynamical phase transitions. A connection between equilibrium phase transitions and nonequilibrium behaviors of the system is disclosed in terms of the quantum Fisher information. We also demonstrate that near the critical points parameter estimation beyond the standard quantum limit can be implemented. This work not only advances the exploration of excited-state quantum phase transitions via a scheme that can immediately be applied to a broad class of few-mode quantum systems, but also provides a new perspective on the relationship between quantum criticality and quantum enhanced sensing.

Stability and dynamics across magnetic phases of vortex-bright type excitations in spinor Bose-Einstein condensates

The static properties, i.e., existence and stability, as well as the quench-induced dynamics of vortex-bright type excitations in two-dimensional harmonically confined spin-1 Bose-Einstein condensates are investigated. Linearly stable vortex-bright-vortex and bright-vortex-bright solutions arise in both antiferromagnetic and ferromagnetic spinor gases upon quadratic Zeeman energy shift variations. Their deformations across the relevant transitions are exposed and discussed in detail evincing also that emergent instabilities can lead to pattern formation. Spatial elongations, precessional motion and spiraling of the nonlinear excitations when exposed to finite temperatures and upon crossing the distinct phase boundaries, via quenching of the quadratic Zeeman coefficient, are unveiled. Spin-mixing processes triggered by the quench lead, among others, to changes in the waveform of the ensuing configurations. Our findings reveal an interplay between pattern formation and spin-mixing processes being accessible in contemporary cold atom experiments.

Stationary solutions and dynamical evolution of the nonlocal Gross–Pitaevskii equation in spin-2 Bose–Einstein condensates

In this paper, we investigate the nonlocal Gross–Pitaevskii equation which describes the phenomena of Bose–Einstein condensates under the mean field approximation. Using mean-field theory and adopting separation of variables method, the five-component Gross–Pitaevskii spin–orbit-coupled spin-2 Bose–Einstein condensate model can be reduced to five-component ordinary differential equation, then twelve families of solutions are obtained by the combination of some Jacobi elliptic functions. In particular, when the modulus of Jacobi elliptic function tends to one, a series of bright soliton and dark soliton and their combined solution are obtained. These periodic and hyperbolic soliton solutions are analyzed in detail, the nature and images will be of practical application to provide theoretical guidance for spin systems.