Coherent control via periodic modulation, also known as Floquet engineering, has emerged as a powerful experimental method for the realization of novel quantum systems with exotic properties. In ...particular, it has been employed to study topological phenomena in a variety of different platforms. In driven systems, the topological properties of the quasienergy bands can often be determined by standard topological invariants, such as Chern numbers, which are commonly used in static systems. However, due to the periodic nature of the quasienergy spectrum, this topological description is incomplete and new invariants are required to fully capture the topological properties of these driven settings. Most prominently, there are two-dimensional anomalous Floquet systems that exhibit robust chiral edge modes, despite all Chern numbers being equal to zero. Here we realize such a system with bosonic atoms in a periodically driven honeycomb lattice and infer the complete set of topological invariants from energy gap measurements and local Hall deflections.Standard topological invariants commonly used in static systems are not enough to fully capture the topological properties of Floquet systems. In a periodically driven quantum gas, chiral edge modes emerge despite all Chern numbers being equal to zero.
Quantum simulation has the potential to investigate gauge theories in strongly interacting regimes, which are currently inaccessible through conventional numerical techniques. Here, we take a first ...step in this direction by implementing a Floquet-based method for studying \{\Bbb Z}_2\ lattice gauge theories using two-component ultracold atoms in a double-well potential. For resonant periodic driving at the on-site interaction strength and an appropriate choice of the modulation parameters, the effective Floquet Hamiltonian exhibits \{\Bbb Z}_2\ symmetry. We study the dynamics of the system for different initial states and critically contrast the observed evolution with a theoretical analysis of the full time-dependent Hamiltonian of the periodically driven lattice model. We reveal challenges that arise due to symmetry-breaking terms and outline potential pathways to overcome these limitations. Our results provide important insights for future studies of lattice gauge theories based on Floquet techniques.
Single atoms and molecules can be trapped in tightly focused beams of light that form ‘optical tweezers’, affording exquisite capabilities for the control and detection of individual particles. This ...approach has progressed to creating tweezer arrays holding hundreds of atoms, resulting in a platform for controlling large many-particle quantum systems. Here we review this new approach to microscopic control of scalable atomic and molecular neutral quantum systems, its future prospects, and applications in quantum information processing, quantum simulation and metrology.Large arrays of atoms and molecules can be arranged and controlled with high precision using optical tweezers. This Review surveys the latest methodological advances and their applications to quantum technologies.
Quantum simulation, a subdiscipline of quantum computation, can provide valuable insight into difficult quantum problems in physics or chemistry. Ultracold atoms in optical lattices represent an ...ideal platform for simulations of quantum many-body problems. Within this setting, quantum gas microscopes enable single atom observation and manipulation in large samples. Ultracold atom–based quantum simulators have already been used to probe quantum magnetism, to realize and detect topological quantum matter, and to study quantum systems with controlled long-range interactions. Experiments on many-body systems out of equilibrium have also provided results in regimes unavailable to the most advanced supercomputers. We review recent experimental progress in this field and comment on future directions.
Open physical systems with balanced loss and gain, described by non-Hermitian parity-time Formula: see text reflection symmetric Hamiltonians, exhibit a transition which could engender modes that ...exponentially decay or grow with time, and thus spontaneously breaks the Formula: see text-symmetry. Such Formula: see text-symmetry-breaking transitions have attracted many interests because of their extraordinary behaviors and functionalities absent in closed systems. Here we report on the observation of Formula: see text-symmetry-breaking transitions by engineering time-periodic dissipation and coupling, which are realized through state-dependent atom loss in an optical dipole trap of ultracold
Li atoms. Comparing with a single transition appearing for static dissipation, the time-periodic counterpart undergoes Formula: see text-symmetry breaking and restoring transitions at vanishingly small dissipation strength in both single and multiphoton transition domains, revealing rich phase structures associated to a Floquet open system. The results enable ultracold atoms to be a versatile tool for studying Formula: see text-symmetric quantum systems.
Quantum dynamics induced in quenching a d-dimensional topological phase across a phase transition may exhibit a nontrivial dynamical topological pattern on the (d−1)D momentum subspace, called band ...inversion surfaces (BISs), which have a one-to-one correspondence to the bulk topology of the postquench phase. Here we report the experimental observation of such dynamical bulk-surface correspondence through measuring the topological charges in a 2D quantum anomalous Hall model realized in an optical Raman lattice. The system can be quenched with respect to every spin axis by suddenly varying the two-photon detuning or phases of the Raman couplings, in which the topological charges and BISs are measured dynamically by the time-averaged spin textures. We observe that the total charges in the region enclosed by BISs define a dynamical topological invariant, which equals the Chern number of the postquench band and also characterizes the topological pattern of a dynamical field emerging on the BISs, rendering the dynamical bulk-surface correspondence. This study opens a new avenue to explore topological phases dynamically.
Full text
Available for:
CMK, CTK, FMFMET, NUK, UL
Lowering the entropy
Atoms loaded in an optical lattice can convincingly mimic the behavior of electrons in solids. However, reaching very low temperatures, where the most interesting quantum phases ...are expected to occur, is tricky. Yang
et al.
introduced a clever experimental technique to reduce the entropy of their sample. They created an array consisting of alternating rows of sample atoms and reservoirs. The entropy was transferred from the sample atoms to the adjacent reservoirs, which were then removed. The resulting low-entropy system can be used as a basis for quantum simulation and information.
Science
, this issue p.
550
An entropy redistribution scheme is developed for applications in quantum simulation and information processing.
Scalable, coherent many-body systems can enable the realization of previously unexplored quantum phases and have the potential to exponentially speed up information processing. Thermal fluctuations are negligible and quantum effects govern the behavior of such systems with extremely low temperature. We report the cooling of a quantum simulator with 10,000 atoms and mass production of high-fidelity entangled pairs. In a two-dimensional plane, we cool Mott insulator samples by immersing them into removable superfluid reservoirs, achieving an entropy per particle of
1.9
−
0.4
+
1.7
×
10
−
3
k
B
. The atoms are then rearranged into a two-dimensional lattice free of defects. We further demonstrate a two-qubit gate with a fidelity of 0.993 ± 0.001 for entangling 1250 atom pairs. Our results offer a setting for exploring low-energy many-body phases and may enable the creation of large-scale entanglement.
PDF
