arXiv subjects

Brandon M. Anderson

Publications and source records attributed to Brandon M. Anderson.

27 records · Page 2Linked to original sources

arXiv2014

Ring model for trapped condensates with synthetic spin-orbit coupling

We derive an effective ring model in momentum space for trapped bosons with synthetic spin-orbit coupling. This effective model is characterized by a peculiar form of the inter particle interactions, which is crucially modified by the external confinement. The ring model allows for an intuitive understanding of the phase diagram of trapped condensates with isotropic spin-orbit coupling, and in particular for the existence of skyrmion lattice phases. The model, which may be generally applied for spinor condensates of arbitrary spin and spin-dependent interactions, is illustrated for the particular cases of spin-1/2 and spin-1 condensates.

cond-mat.quant-gas↗

arXiv2014

Half-Quantum Vortex Molecules in a Binary Dipolar Bose Gas

We study the ground state phases of a rotating two-component, or binary Bose-Einstein condensate, wherein one component possesses a large magnetic dipole moment. A variety of non-trivial phases emerge in this system, including a half-quantum vortex (HQV) chain phase and a HQV molecule phase, where HQVs of opposite charge bind at short distances. We attribute the emergence of these phases to the development of a minimum in the adiabatic HQV interaction potential, which we calculate explicitly. We thus show that the presence of dipolar interactions in this system leads to a rich phase diagram, and the formation of HQV molecules.

cond-mat.quant-gas↗

arXiv2013

Meron Ground State of Rashba Spin-Orbit-Coupled Dipolar Bosons

We study the effects of dipolar interactions on a Bose-Einstein condensate with synthetically generated Rashba spin-orbit coupling. The dipolar interaction we consider includes terms that couple spin and orbital angular momentum in a way perfectly congruent with the single-particle Rashba coupling. We show that this internal spin-orbit coupling plays a crucial role in the rich ground-state phase diagram of the trapped condensate. In particular, we predict the emergence of a thermodynamically stable ground state with a meron spin configuration.

cond-mat.quant-gas↗

arXiv2013

Magnetically generated spin-orbit coupling for ultracold atoms

We present a new technique for producing two- and three-dimensional Rashba-type spin-orbit couplings for ultracold atoms without involving light. The method relies on a sequence of pulsed inhomogeneous magnetic fields imprinting suitable phase gradients on the atoms. For sufficiently short pulse durations, the time-averaged Hamiltonian well approximates the Rashba Hamiltonian. Higher order corrections to the energy spectrum are calculated exactly for spin-1/2 and perturbatively for higher spins. The pulse sequence does not modify the form of rotationally symmetric atom-atom interactions. Finally, we present a straightforward implementation of this pulse sequence on an atom chip.

cond-mat.quant-gas↗

arXiv2012

Three-Dimensional Spin-Orbit Coupling in a Trap

We investigate the properties of an atom under the influence of a synthetic three-dimensional spin-orbit coupling (Weyl coupling) in the presence of a harmonic trap. The conservation of total angular momentum provides a numerically efficient scheme for finding the spectrum and eigenfunctions of the system. We show that at large spin-orbit coupling the system undergoes dimensional reduction from three to one dimension at low energies, and the spectrum is approximately Landau level-like. At high energies, the spectrum is approximately given by the three-dimensional isotropic harmonic oscillator. We explore the properties of the ground state in both position and momentum space. We find the ground state has spin textures with oscillations set by the spin-orbit length scale.

cond-mat.quant-gas↗

arXiv2012

Synthetic 3D Spin-Orbit Coupling

We describe a method for creating a three-dimensional analogue to Rashba spin-orbit coupling in systems of ultracold atoms. This laser induced coupling uses Raman transitions to link four internal atomic states with a tetrahedral geometry, and gives rise to a Dirac point that is robust against environmental perturbations. We present an exact result showing that such a spin-orbit coupling in a fermionic system always rise to a molecular bound state.

cond-mat.quant-gas↗

arXiv2011

Low-density molecular gas of tightly-bound Rashba-Dresselhaus fermions

We study interacting Rashba-Dresselhaus fermions in two spatial dimensions. First, we present a new exact solution to the two-particle pairing problem of spin-orbit-coupled fermions for arbitrary Rashba and Dresselhaus spin-orbit interactions. An exact molecular wave function and the Green function are explicitly derived along with the binding energy and the spectrum of the molecular state. In the second part, we consider a thermal Boltzmann gas of fermionic molecules and compute the time-of-flight velocity and spin distributions for a single fermion in the gas. We show that the pairing signatures can be observed already in the first-moment expectation values, such as time-of-flight density and spin profiles.

cond-mat.quant-gas↗

arXiv2010

Interferometry with Synthetic Gauge Fields

We propose a compact atom interferometry scheme for measuring weak, time-dependent accelerations. Our proposal uses an ensemble of dilute trapped bosons with two internal states that couple to a synthetic gauge field with opposite charges. The trapped gauge field couples spin to momentum to allow time dependent accelerations to be continuously imparted on the internal states. We generalize this system to reduce noise and estimate the sensitivity of such a system to be S~10^-7 m / s^2 / Hz^1/2.

quant-ph↗

arXiv2005

Polarization Requirements for Ensemble Implementations of Quantum Algorithms with a Single Bit Output

We compare the failure probabilities of ensemble implementations of quantum algorithms which use pseudo-pure initial states, quantified by their polarization, to those of competing classical probabilistic algorithms. Specifically we consider a class algorithms which require only one bit to output the solution to problems. For large ensemble sizes, we present a general scheme to determine a critical polarization beneath which the quantum algorithm fails with greater probability than its classical competitor. We apply this to the Deutsch-Jozsa algorithm and show that the critical polarization is 86.6%.

quant-ph↗