25 research outputs found
Simulation of quantum dynamics with quantum optical systems
We propose the use of quantum optical systems to perform universal simulation
of quantum dynamics. Two specific implementations that require present
technology are put forward for illustrative purposes. The first scheme consists
of neutral atoms stored in optical lattices, while the second scheme consists
of ions stored in an array of micro--traps. Each atom (ion) supports a
two--level system, on which local unitary operations can be performed through a
laser beam. A raw interaction between neighboring two--level systems is
achieved by conditionally displacing the corresponding atoms (ions). Then,
average Hamiltonian techniques are used to achieve evolutions in time according
to a large class of Hamiltonians.Comment: 14 pages, 6 figure
Quantum computation with cold bosonic atoms in an optical lattice
We analyse an implementation of a quantum computer using bosonic atoms in an
optical lattice. We show that, even though the number of atoms per site and the
tunneling rate between neighbouring sites is unknown, one may perform a
universal set of gates by means of adiabatic passage
Efficient quantum simulation of fermionic and bosonic models in trapped ions
We analyze the efficiency of quantum simulations of fermionic and bosonic
models in trapped ions. In particular, we study the optimal time of entangling
gates and the required number of total elementary gates. Furthermore, we
exemplify these estimations in the light of quantum simulations of quantum
field theories, condensed-matter physics, and quantum chemistry. Finally, we
show that trapped-ion technologies are a suitable platform for implementing
quantum simulations involving interacting fermionic and bosonic modes, paving
the way for overcoming classical computers in the near future.Comment: 13 pages, 3 figures. Published in EPJ Quantum Technolog
Digital-analog quantum simulation of generalized Dicke models with superconducting circuits
We propose a digital-analog quantum simulation of generalized Dicke models
with superconducting circuits, including Fermi-Bose condensates, biased and
pulsed Dicke models, for all regimes of light-matter coupling. We encode these
classes of problems in a set of superconducting qubits coupled with a bosonic
mode implemented by a transmission line resonator. Via digital-analog
techniques, an efficient quantum simulation can be performed in
state-of-the-art circuit quantum electrodynamics platforms, by suitable
decomposition into analog qubit-bosonic blocks and collective single-qubit
pulses through digital steps. Moreover, just a single global analog block would
be needed during the whole protocol in most of the cases, superimposed with
fast periodic pulses to rotate and detune the qubits. Therefore, a large number
of digital steps may be attained with this approach, providing a reduced
digital error. Additionally, the number of gates per digital step does not grow
with the number of qubits, rendering the simulation efficient. This strategy
paves the way for the scalable digital-analog quantum simulation of many-body
dynamics involving bosonic modes and spin degrees of freedom with
superconducting circuits.Comment: Published version, with added reference
Fragmented superfluid due to frustration of cold atoms in optical lattices
A one dimensional optical lattice is considered where a second dimension is
encoded in the internal states of the atoms giving effective ladder systems.
Frustration is introduced by an additional optical lattice that induces
tunneling of superposed atomic states. The effects of frustration range from
the stabilization of the Mott insulator phase with ferromagnetic order, to the
breakdown of superfluidity and the formation of a macroscopically fragmented
phase.Comment: New version, more results, about 20 page
Controlled Collisions for Multiparticle Entanglement of Optically Trapped Atoms
Entanglement lies at the heart of quantum mechanics and in recent years has
been identified as an essential resource for quantum information processing and
computation. Creating highly entangled multi-particle states is therefore one
of the most challenging goals of modern experimental quantum mechanics,
touching fundamental questions as well as practical applications. Here we
report on the experimental realization of controlled collisions between
individual neighbouring neutral atoms trapped in the periodic potential of an
optical lattice. These controlled interactions act as an array of quantum gates
between neighbouring atoms in the lattice and their massively parallel
operation allows the creation of highly entangled states in a single
operational step, independent of the size of the system. In the experiment, we
observe a coherent entangling-disentangling evolution in the many-body system
depending on the phase shift acquired during the collision between neighbouring
atoms. This dynamics is indicative of highly entangled many-body states that
present novel opportunities for theory and experiment.Comment: 17 pages, including 5 figures, accepted for publication in Natur
Simulating open quantum systems: from many-body interactions to stabilizer pumping
In a recent experiment, Barreiro et al. demonstrated the fundamental building
blocks of an open-system quantum simulator with trapped ions [Nature 470, 486
(2011)]. Using up to five ions, single- and multi-qubit entangling gate
operations were combined with optical pumping in stroboscopic sequences. This
enabled the implementation of both coherent many-body dynamics as well as
dissipative processes by controlling the coupling of the system to an
artificial, suitably tailored environment. This engineering was illustrated by
the dissipative preparation of entangled two- and four-qubit states, the
simulation of coherent four-body spin interactions and the quantum
non-demolition measurement of a multi-qubit stabilizer operator. In the present
paper, we present the theoretical framework of this gate-based ("digital")
simulation approach for open-system dynamics with trapped ions. In addition, we
discuss how within this simulation approach minimal instances of spin models of
interest in the context of topological quantum computing and condensed matter
physics can be realized in state-of-the-art linear ion-trap quantum computing
architectures. We outline concrete simulation schemes for Kitaev's toric code
Hamiltonian and a recently suggested color code model. The presented simulation
protocols can be adapted to scalable and two-dimensional ion-trap
architectures, which are currently under development.Comment: 27 pages, 9 figures, submitted to NJP Focus on Topological Quantum
Computatio