Characterizing the phase diagram of finite-size dipolar Bose-Hubbard systems

Abstract

We use state-of-the-art density matrix renormalization group calculations in the canonical ensemble to determine the phase diagram of the dipolar Bose-Hubbard model on a finite cylinder. We consider several observables that are accessible in typical optical lattice setups and assess how well these quantities perform as order parameters. We find that, especially for small systems, the occupation imbalance is less susceptible to boundary effects than the structure factor in uncovering the presence of a periodic density modulation. By analysing the non-local correlations, we find that the appearance of supersolid order is very sensitive to boundary effects, which may render it difficult to observe in quantum gas lattice experiments with a few tens of particles. Finally, we show how density measurements readily obtainable on a quantum gas microscope allow distinguishing between superfluid and solid phases using unsupervised machine-learning techniques. arXiv:1909.09099v1 [cond-mat.quant-gas]

Robust entangling gate for polar molecules using magnetic and microwave fields

“…Our tools for controlling the states of single molecules and molecular pairs may be applied to advance other quantum technologies with polar molecules. For example, the possibility of controlling molecular EDMs with easily accessible magnetic and MW fields will expand the range of models that can be simulated using ultracold molecules [27][28][29][30][31][32]. In addition, shaped MW pulses will allow fast control of state-dependent interactions between molecules.…”

“…The field of ultracold molecules has seen enormous progress in the past few years, with landmark achievements such as the production of the first quantum-degenerate molecular Fermi gas [1], low-entropy molecular samples in optical lattices [2,3], trapping of single molecules in optical tweezers [4][5][6], and magneto-optical trapping and sub-Doppler cooling of molecules [7][8][9][10][11]. These results bring significantly closer a broad range of applications of ultracold molecules, from state-controlled chemistry [12][13][14][15][16][17] and novel tests of fundamental laws of nature [18][19][20][21] to new architectures for quantum computation [22][23][24][25][26], quantum simulation [27][28][29][30][31][32], and quantum sensing [33,34].…”

Anomalous Spin-Charge Separation in a Driven Hubbard System

“…We removeV 2D at time τ ¼ 0, and we use exact diagonalization to fully describe the quick growth of entanglement in the quenched system [57]. To monitor the spin and density dynamics, we compute density and spin imbalances defined as [60][61][62][63] I O ðτÞ ¼ X j x ;j y ð−1Þ j x þj y hÔ j ðτÞi; O¼ n; s: ð6Þ…”

Dipolar Bose-Hubbard Model in finite-size real-space cylindrical lattices

“…These quantities are accessible numerically through the eigenvalues and elements of the one-body density-matrix b † z1,c1 bz2,c2 respectively. Specifically, we define the difference δ e between the population fractions in the dominant two modes, which gives δ e = 1 in a perfect condensate and δ e = 0 in a solid [40]. Again, we define sublattice-resolved versions of this order parameter, where δ e,E (δ e,P ) denotes the difference in population fraction on the polar(equatorial) sublattice between the two modes with the greatest population on that sublattice.…”

“…Peaks in entanglement entropy can be used to pinpoint transitions between superfluid and density wave states without choosing the order parameters for the phases in advance [40][41][42]. The first derivative of entanglement entropy (and other entanglement measures) has also been used to locate transitions which do not feature discontinuities in order parameters [43][44][45].…”