23,009 research outputs found
Modelling chemical reactions using semiconductor quantum dots
We propose using semiconductor quantum dots for a simulation of chemical
reactions as electrons are redistributed among such artificial atoms. We show
that it is possible to achieve various reaction regimes and obtain different
reaction products by varying the speed of voltage changes applied to the gates
forming quantum dots. Considering the simplest possible reaction, , we show how the necessary initial state can be obtained and what
voltage pulses should be applied to achieve a desirable final product. Our
calculations have been performed using the Pechukas gas approach, which can be
extended for more complicated reactions
Switchable coupling for superconducting qubits using double resonance in the presence of crosstalk
Several methods have been proposed recently to achieve switchable coupling
between superconducting qubits. We discuss some of the main considerations
regarding the feasibility of implementing one of those proposals: the
double-resonance method. We analyze mainly issues related to the achievable
effective coupling strength and the effects of crosstalk on this coupling
approach. We also find a new, crosstalk-assisted coupling channel that can be
an attractive alternative when implementing the double-resonance coupling
proposal.Comment: 4 pages, 3 figure
An Evidence Based Time-Frequency Search Method for Gravitational Waves from Pulsar Glitches
We review and expand on a Bayesian model selection technique for the
detection of gravitational waves from neutron star ring-downs associated with
pulsar glitches. The algorithm works with power spectral densities constructed
from overlapping time segments of gravitational wave data. Consequently, the
original approach was at risk of falsely identifying multiple signals where
only one signal was present in the data. We introduce an extension to the
algorithm which uses posterior information on the frequency content of detected
signals to cluster events together. The requirement that we have just one
detection per signal is now met with the additional bonus that the belief in
the presence of a signal is boosted by incorporating information from adjacent
time segments.Comment: 6 pages, 4 figures, submitted to AMALDI 7 proceeding
Speed limits for quantum gates in multi-qubit systems
We use analytical and numerical calculations to obtain speed limits for
various unitary quantum operations in multiqubit systems under typical
experimental conditions. The operations that we consider include single-, two-,
and three-qubit gates, as well as quantum-state transfer in a chain of qubits.
We find in particular that simple methods for implementing two-qubit gates
generally provide the fastest possible implementations of these gates. We also
find that the three-qubit Toffoli gate time varies greatly depending on the
type of interactions and the system's geometry, taking only slightly longer
than a two-qubit controlled-NOT (CNOT) gate for a triangle geometry. The speed
limit for quantum-state transfer across a qubit chain is set by the maximum
spin-wave speed in the chain.Comment: 7 pages (two-column), 2 figures, 2 table
Quantum state transfer via temporal kicking of information
We propose a strategy for perfect state transfer in spin chains based on the
use of an unmodulated coupling Hamiltonian whose coefficients are explicitly
time dependent. We show that, if specific and non-demanding conditions are
satisfied by the temporal behavior of the coupling strengths, our model allows
perfect state transfer. The paradigma put forward by our proposal holds the
promises to set an alternative standard to the use of clever encoding and
coupling-strength engineering for perfect state transfer.Comment: 7 pages, 7 figures, RevTeX
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