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Closed-form analytical continuation of spin density interactions in spin-2 superfluids

Jeffrey Yepez

Published Sep 8, 2016• 0 citations
OpenAlex

Abstract

Presented is an unitary operator splitting method for handling the spin-density interaction in spinor Bose-Einstein condensates. The zero temperature behavior of a spinor BEC is given by mean field theory, where the Hamiltonian includes a nonlinear hyperfine spin interaction. This hyperfine interaction has a diagonal probability-density term (leading to the usual Gross-Pitaevskii type equation of motion) but also has a nondiagonal spin-density term. Since the F=2 spinor BEC (spin-2 BEC) has a non-Abelian superfluid phase (nonperturbative cyclic phase in the strong spin-density coupling regime), an infinite-order expansion of the quantum evolution operator is needed for quantum simulation applications. An infinite-order expansion, obtained by analytical continuation and expressed in analytically closed form, for the spin-2 BEC is presented.

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Quantum lattice gas model of spin-2 Bose-Einstein condensates and closed-form analytical continuation of nonlinear interactions in spin-2 superfluids

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Presented is an unitary operator splitting method for handling the spin-density interaction in spinor Bose-Einstein condensates. The zero temperature behavior of a spinor BEC is given by mean field theory, where the Hamiltonian includes a nonlinear hyperfine spin interaction. This hyperfine interaction has a diagonal probability-density term (leading to the usual Gross-Pitaevskii type equation of motion) but also has a nondiagonal spin-density term. Since the F=2 spinor BEC (spin-2 BEC) has a non-Abelian superfluid phase (nonperturbative cyclic phase in the strong spin-density coupling regime), an infinite-order expansion of the quantum evolution operator is needed for quantum simulation applications. An infinite-order expansion, obtained by analytical continuation and expressed in analytically closed form, for the spin-2 BEC is presented.

arXiv:1609.02229•Sep 8, 2016•1 citation

Spin-2 BEC spinor superfluid soliton-soliton scattering in one and two space dimensions

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Presented is a study of a spin-2 Bose-Einstein condensate (BEC) by unitary quantum simulations of time-dependent soliton-soliton scattering. The quantum simulation method is based on a quantum lattice algorithm which is designed for implementation on a future digital quantum computer but is tested today using a parallel computing architecture based on graphical processing units (GPUs). We analytically solve the spin-2 BEC equations of motion, a nonlinear system of 5 coupled Gross-Pitiaevskii (GP) equations, in one- and two-spatial dimensions. In 1D there are 16 bright soliton and 16 dark soliton solutions. In 2D there are 3 dark soliton solutions Pade approximation solutions, for m_f=+/-2, m_f=+/-1 and m_f=0, corresponding to quantum vortices. We report on the implementation the unitary quantum lattice gas algorithm for spinor superfluid and establish its efficacy by validating the stability of the 1D and 2D energy eigenstate solutions of the spin-2 BEC Hamiltonian. Using the calibrated quantum lattice gas algorithm, the highly nonlinear physics in the nonintegrable regime of the spin-2 BEC is studied by performing soliton-soliton scattering experiments. The scattering of topological solitons produces breathers and complex quantum vortices characterized by local entanglement across multiple m_f-hyperfine states of the Zeeman manifold.

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Analytical solutions to the spin-1 Bose–Einstein condensates

Zhi-Hai Zhang, Cong Zhang, Shi-Jie Yang +1 more

We analytically solve the one-dimensional coupled Gross-Pitaevskii equations which govern the motion of F=1 spinor Bose-Einstein condensates. The nonlinear density-density interactions are decoupled by making use of the unique properties of the Jacobian elliptical functions. Several types of complex stationary solutions are deduced. Furthermore, exact non-stationary solutions to the time-dependent Gross-Pitaevskii equations are constructed by making use of the spin-rotational symmetry of the Hamiltonian. The spin-polarizations exhibit kinked configurations. Our method is applicable to other coupled nonlinear systems.

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Stochastic Gross-Pitaevskii theory for a spin-1 Bose gas: Application to superfluidity in two dimensions

Andrew P. C. Underwood, P. B. Blakie

This paper develops and implements the stochastic projected Gross-Pitaevskii equation for spin-1 Bose gases, addressing key considerations for numerical simulations. As an application of the theory we explore equilibrium phases in a two-dimensional spin-1 gas, where quasi-long-range order emerges via a Berezinskii-Kosterlitz-Thouless transition. Our analysis includes the definition of superfluid densities for both mass and spin degrees of freedom in a manner suitable for implementation within a stochastic projected Gross-Pitaevskii equation simulation. We present a finite-temperature phase diagram for the ferromagnetic spin-1 Bose gas and identify three distinct superfluid phases: two exhibiting conventional Berezinskii-Kosterlitz-Thouless-like behavior and an additional phase that simultaneously supports independent mass and spin superflows. As temperature increases, the stability region of this additional phase shrinks. We provide a characterization of the phase transitions through consideration of the spin-component densities and the unbinding of multiple types of vortices. This work provides a foundation for further studies of nonequilibrium and finite-temperature phenomena in spinor Bose gases.

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Analytic models for the density of a ground-state spinor condensate

Sandeep Gautam, Sadhan K. Adhikari

We demonstrate that the ground state of a trapped spin-1 and spin-2 spinor ferromagnetic Bose-Einstein condensate (BEC) can be well approximated by a single decoupled Gross-Pitaevskii (GP) equation. Useful analytic models for the ground-state densities of ferromagnetic BECs are obtained from the Thomas-Fermi approximation (TFA) to this decoupled equation. Similarly, for the ground states of spin-1 antiferromagnetic and spin-2 antiferromagnetic and cyclic BECs, some of the spin-component densities are zero, which reduces the coupled GP equation to a simple reduced form. Analytic models for ground-state densities are also obtained for antiferromagnetic and cyclic BECs from the TFA to the respective reduced GP equations. The analytic densities are illustrated and compared with the full numerical solution of the GP equation with realistic experimental parameters.

arXiv:1507.06883•Physical Review A•Aug 12, 2015•27 citations
Presented is an unitary operator splitting method for handling the spin-density interaction in spinor Bose-Einstein condensates. The zero temperature behavior of a spinor BEC is given by mean field theory, where the Hamiltonian includes a nonlinear hyperfine spin interaction. This hyperfine interaction has a diagonal probability-density term (leading to the usual Gross-Pitaevskii type equation of motion) but also has a nondiagonal spin-density term. Since the F=2 spinor BEC (spin-2 BEC) has a non-Abelian superfluid phase (nonperturbative cyclic phase in the strong spin-density coupling regime), an infinite-order expansion of the quantum evolution operator is needed for quantum simulation applications. An infinite-order expansion, obtained by analytical continuation and expressed in analytically closed form, for the spin-2 BEC is presented.
Presented is an unitary operator splitting method for handling the spin-density interaction in spinor Bose-Einstein condensates. The zero temperature behavior of a spinor BEC is given by mean field theory, where the Hamiltonian includes a nonlinear hyperfine spin interaction. This hyperfine interaction has a diagonal probability-density term (leading to the usual Gross-Pitaevskii type equation of motion) but also has a nondiagonal spin-density term. Since the F=2 spinor BEC (spin-2 BEC) has a non-Abelian superfluid phase (nonperturbative cyclic phase in the strong spin-density coupling regime), an infinite-order expansion of the quantum evolution operator is needed for quantum simulation applications. An infinite-order expansion, obtained by analytical continuation and expressed in analytically closed form, for the spin-2 BEC is presented.
Presented is a study of a spin-2 Bose-Einstein condensate (BEC) by unitary quantum simulations of time-dependent soliton-soliton scattering. The quantum simulation method is based on a quantum lattice algorithm which is designed for implementation on a future digital quantum computer but is tested today using a parallel computing architecture based on graphical processing units (GPUs). We analytically solve the spin-2 BEC equations of motion, a nonlinear system of 5 coupled Gross-Pitiaevskii (GP) equations, in one- and two-spatial dimensions. In 1D there are 16 bright soliton and 16 dark soliton solutions. In 2D there are 3 dark soliton solutions Pade approximation solutions, for m_f=+/-2, m_f=+/-1 and m_f=0, corresponding to quantum vortices. We report on the implementation the unitary quantum lattice gas algorithm for spinor superfluid and establish its efficacy by validating the stability of the 1D and 2D energy eigenstate solutions of the spin-2 BEC Hamiltonian. Using the calibrated quantum lattice gas algorithm, the highly nonlinear physics in the nonintegrable regime of the spin-2 BEC is studied by performing soliton-soliton scattering experiments. The scattering of topological solitons produces breathers and complex quantum vortices characterized by local entanglement across multiple m_f-hyperfine states of the Zeeman manifold.
We analytically solve the one-dimensional coupled Gross-Pitaevskii equations which govern the motion of F=1 spinor Bose-Einstein condensates. The nonlinear density-density interactions are decoupled by making use of the unique properties of the Jacobian elliptical functions. Several types of complex stationary solutions are deduced. Furthermore, exact non-stationary solutions to the time-dependent Gross-Pitaevskii equations are constructed by making use of the spin-rotational symmetry of the Hamiltonian. The spin-polarizations exhibit kinked configurations. Our method is applicable to other coupled nonlinear systems.
A finite temperature hydrodynamic model is derived for the spin-1 ultracold bosons by the many-particle quantum hydrodynamic method. It is presented as the two fluid model of the Bose–Einstein condensate (BEC) and normal fluid. The continuity, Euler, spin evolution, and nematic tensor evolution equations are derived for each fluid. The linear and quadratic Zeeman effects are included. Scalar and spin–spin like short-range interactions are considered in the first order by the interaction radius. Obtained hydrodynamic equations are also represented as the set of two nonlinear Pauli equations. The spectrum of the bulk collective excitations is considered for the ferromagnetic phase in the small temperature limit. The spin wave is not affected by the presence of the small temperature in the described minimal coupling model, where the thermal part of the spin-current of the normal fluid is neglected. The two sound waves are affected by the spin evolution in the same way as the change of spectrum of the single sound wave in BEC, where speed of sound is proportional to g1+g2 with gi as the interaction constants.
This paper develops and implements the stochastic projected Gross-Pitaevskii equation for spin-1 Bose gases, addressing key considerations for numerical simulations. As an application of the theory we explore equilibrium phases in a two-dimensional spin-1 gas, where quasi-long-range order emerges via a Berezinskii-Kosterlitz-Thouless transition. Our analysis includes the definition of superfluid densities for both mass and spin degrees of freedom in a manner suitable for implementation within a stochastic projected Gross-Pitaevskii equation simulation. We present a finite-temperature phase diagram for the ferromagnetic spin-1 Bose gas and identify three distinct superfluid phases: two exhibiting conventional Berezinskii-Kosterlitz-Thouless-like behavior and an additional phase that simultaneously supports independent mass and spin superflows. As temperature increases, the stability region of this additional phase shrinks. We provide a characterization of the phase transitions through consideration of the spin-component densities and the unbinding of multiple types of vortices. This work provides a foundation for further studies of nonequilibrium and finite-temperature phenomena in spinor Bose gases.
We demonstrate that the ground state of a trapped spin-1 and spin-2 spinor ferromagnetic Bose-Einstein condensate (BEC) can be well approximated by a single decoupled Gross-Pitaevskii (GP) equation. Useful analytic models for the ground-state densities of ferromagnetic BECs are obtained from the Thomas-Fermi approximation (TFA) to this decoupled equation. Similarly, for the ground states of spin-1 antiferromagnetic and spin-2 antiferromagnetic and cyclic BECs, some of the spin-component densities are zero, which reduces the coupled GP equation to a simple reduced form. Analytic models for ground-state densities are also obtained for antiferromagnetic and cyclic BECs from the TFA to the respective reduced GP equations. The analytic densities are illustrated and compared with the full numerical solution of the GP equation with realistic experimental parameters.