14,981 research outputs found
Imprinting Patterns of Neutral Atoms in an Optical Lattice using Magnetic Resonance Techniques
We prepare arbitrary patterns of neutral atoms in a one-dimensional (1D)
optical lattice with single-site precision using microwave radiation in a
magnetic field gradient. We give a detailed account of the current limitations
and propose methods to overcome them. Our results have direct relevance for
addressing of planes, strings or single atoms in higher dimensional optical
lattices for quantum information processing or quantum simulations with
standard methods in current experiments. Furthermore, our findings pave the way
for arbitrary single qubit control with single site resolution.Comment: 9 pages, 7 figure
Quantum computing implementations with neutral particles
We review quantum information processing with cold neutral particles, that
is, atoms or polar molecules. First, we analyze the best suited degrees of
freedom of these particles for storing quantum information, and then we discuss
both single- and two-qubit gate implementations. We focus our discussion mainly
on collisional quantum gates, which are best suited for atom-chip-like devices,
as well as on gate proposals conceived for optical lattices. Additionally, we
analyze schemes both for cold atoms confined in optical cavities and hybrid
approaches to entanglement generation, and we show how optimal control theory
might be a powerful tool to enhance the speed up of the gate operations as well
as to achieve high fidelities required for fault tolerant quantum computation.Comment: 19 pages, 12 figures; From the issue entitled "Special Issue on
Neutral Particles
High-fidelity quantum driving
The ability to accurately control a quantum system is a fundamental
requirement in many areas of modern science such as quantum information
processing and the coherent manipulation of molecular systems. It is usually
necessary to realize these quantum manipulations in the shortest possible time
in order to minimize decoherence, and with a large stability against
fluctuations of the control parameters. While optimizing a protocol for speed
leads to a natural lower bound in the form of the quantum speed limit rooted in
the Heisenberg uncertainty principle, stability against parameter variations
typically requires adiabatic following of the system. The ultimate goal in
quantum control is to prepare a desired state with 100% fidelity. Here we
experimentally implement optimal control schemes that achieve nearly perfect
fidelity for a two-level quantum system realized with Bose-Einstein condensates
in optical lattices. By suitably tailoring the time-dependence of the system's
parameters, we transform an initial quantum state into a desired final state
through a short-cut protocol reaching the maximum speed compatible with the
laws of quantum mechanics. In the opposite limit we implement the recently
proposed transitionless superadiabatic protocols, in which the system perfectly
follows the instantaneous adiabatic ground state. We demonstrate that
superadiabatic protocols are extremely robust against parameter variations,
making them useful for practical applications.Comment: 17 pages, 4 figure
Collateral coupling between superconducting resonators: Fast and high fidelity generation of qudit-qudit entanglement
Superconducting circuits are highly controllable platforms to manipulate
quantum states, which make them particularly promising for quantum information
processing. We here show how the existence of a distance-independent
interaction between microwave resonators coupled capacitively through a qubit
offers a new control parameter toward this goal. This interaction is able to
induce an idling point between resonant resonators, and its state-dependent
nature allows one to control the flow of information between the resonators.
The advantage of this scheme over previous one is demonstrated through the
generation of high-fidelity NOON states between the resonators, with a lower
number of operations than previous schemes. Beyond superconducting circuits,
our proposal could also apply to atomic lattices with clock transitions in
optical cavities, for example
Ultracold molecules: vehicles to scalable quantum information processing
We describe a novel scheme to implement scalable quantum information
processing using Li-Cs molecular state to entangle Li and Cs
ultracold atoms held in independent optical lattices. The Li atoms will
act as quantum bits to store information, and Cs atoms will serve as
messenger bits that aid in quantum gate operations and mediate entanglement
between distant qubit atoms. Each atomic species is held in a separate optical
lattice and the atoms can be overlapped by translating the lattices with
respect to each other. When the messenger and qubit atoms are overlapped,
targeted single spin operations and entangling operations can be performed by
coupling the atomic states to a molecular state with radio-frequency pulses. By
controlling the frequency and duration of the radio-frequency pulses,
entanglement can either be created or swapped between a qubit messenger pair.
We estimate operation fidelities for entangling two distant qubits and discuss
scalability of this scheme and constraints on the optical lattice lasers
Moir\'e excitons: from programmable quantum emitter arrays to spin-orbit coupled artificial lattices
Highly uniform and ordered nanodot arrays are crucial for high performance
quantum optoelectronics including new semiconductor lasers and single photon
emitters, and for synthesizing artificial lattices of interacting
quasiparticles towards quantum information processing and simulation of
many-body physics. Van der Waals heterostructures of 2D semiconductors are
naturally endowed with an ordered nanoscale landscape, i.e. the moir\'e pattern
that laterally modulates electronic and topographic structures. Here we find
these moir\'e effects realize superstructures of nanodot confinements for
long-lived interlayer excitons, which can be either electrically or strain
tuned from perfect arrays of quantum emitters to excitonic superlattices with
giant spin-orbit coupling (SOC). Besides the wide range tuning of emission
wavelength, the electric field can also invert the spin optical selection rule
of the emitter arrays. This unprecedented control arises from the gauge
structure imprinted on exciton wavefunctions by the moir\'e, which underlies
the SOC when hopping couples nanodots into superlattices. We show that the
moir\'e hosts complex-hopping honeycomb superlattices, where exciton bands
feature a Dirac node and two Weyl nodes, connected by spin-momentum locked
topological edge modes.Comment: To appear in Science Advance
Summer School on Quantum Many-Body Physics of Ultra-Cold Atoms and Molecules
The aim of this School was to bring together both leading scientists from all over the world to discuss current frontiers of research in ultra-cold atomic and molecular gases and young PhD students, postdocs, researchers working on ultra-cold gases. The program focused on the analysis of novel quantum phases and quantum phase transitions in mono-atomic gases, mixtures of fermionic and bosonic atoms in traps and optical lattices and its applications to quantum information processing and metrology. In particular, ultra-cold gases have been used to simulate many known condensed matter phenomena such as superfluid-insulator transitions, BEC-BCS crossover, Anderson localization with unprecedented control. In addition, the ultra-cold atomic and molecular gases reveal completely new phenomena which are not possible to realize in standard condensed-matter systems, since interactions, hopping, dimensionality and temperature can be fully controlled in traps and optical lattices.
The School program combined lectures that pedagogically summarize the main challenges and recent results on each area with short presentations, especially from students and postdocs. We organized a computer based laboratory to make some practice on the numerical simulations of many-body physics of ultracold-cold gases, giving particular importance in this session to quantum Monte Carlo simulations, which are widely used in the context of ultra-cold atomic physics. Poster sessions have been organized
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