369 research outputs found
Quantum Metropolis Sampling
The original motivation to build a quantum computer came from Feynman who
envisaged a machine capable of simulating generic quantum mechanical systems, a
task that is believed to be intractable for classical computers. Such a machine
would have a wide range of applications in the simulation of many-body quantum
physics, including condensed matter physics, chemistry, and high energy
physics. Part of Feynman's challenge was met by Lloyd who showed how to
approximately decompose the time-evolution operator of interacting quantum
particles into a short sequence of elementary gates, suitable for operation on
a quantum computer. However, this left open the problem of how to simulate the
equilibrium and static properties of quantum systems. This requires the
preparation of ground and Gibbs states on a quantum computer. For classical
systems, this problem is solved by the ubiquitous Metropolis algorithm, a
method that basically acquired a monopoly for the simulation of interacting
particles. Here, we demonstrate how to implement a quantum version of the
Metropolis algorithm on a quantum computer. This algorithm permits to sample
directly from the eigenstates of the Hamiltonian and thus evades the sign
problem present in classical simulations. A small scale implementation of this
algorithm can already be achieved with today's technologyComment: revised versio
On the fidelity of two pure states
The fidelity of two pure states (also known as transition probability) is a
symmetric function of two operators, and well-founded operationally as an event
probability in a certain preparation-test pair. Motivated by the idea that the
fidelity is the continuous quantum extension of the combinatorial equality
function, we enquire whether there exists a symmetric operational way of
obtaining the fidelity. It is shown that this is impossible. Finally, we
discuss the optimal universal approximation by a quantum operation.Comment: LaTeX2e, 8 pages, submitted to J. Phys. A: Math. and Ge
Activating NPPT distillation with an infinitesimal amount of bound entanglement
We show that bipartite quantum states of any dimension, which do not have a
positive partial transpose, become 1-distillable when one adds an infinitesimal
amount of bound entanglement. To this end we investigate the activation
properties of a new class of symmetric bound entangled states of full rank. It
is shown that in this set there exist universal activator states capable of
activating the distillation of any NPPT state.Comment: 4 pages, revtex4, 1 figure, references correcte
Neotectonic markers in the Panafrican belt formations of Cameroon: elements of interpretation and their environmental impacts
The North equatorial Panafrican Belt,
whose Cameroonian formations are
dated between 650 and 400 million
years, and which are located in the
North of the Congo Craton, is subdivided
in to three major geodynamic domains:
a north Cameroon domain, a
central Cameroon domain and a south
Cameroon domain. These major domains
are generally, particularly the
central domain, affected by great strikeslip
faults in which the most important
are the central cameroonian shear zone
and the Sanaga fault.
Studies that establish the order of occurrence
of geological events, generally
performed in these domains and particularly
at Banefo area (West Cameroon)
reveal markers of recent tectonics (post
panafrican) that affect the granitogneissic
basement...conferenc
Concurrence Vectors in Arbitrary Multipartite Quantum Systems
For a given pure state of multipartite system, the concurrence vector is
defined by employing the defining representation of generators of the
corresponding rotation groups. The norm of concurrence vector is considered as
a measure of entanglement. For multipartite pure state, the concurrence vector
is regarded as the direct sum of concurrence subvectors in the sense that each
subvector is associated with a pair of particles. It is proposed to use the
norm of each subvector as the contribution of the corresponding pair in
entanglement of the system.Comment: 9 pages, v3, section 3 is revise
Conversion of a general quantum stabilizer code to an entanglement distillation protocol
We show how to convert a quantum stabilizer code to a one-way or two-way
entanglement distillation protocol. The proposed conversion method is a
generalization of those of Shor-Preskill and Nielsen-Chuang. The recurrence
protocol and the quantum privacy amplification protocol are equivalent to the
protocols converted from [[2,1]] stabilizer codes. We also give an example of a
two-way protocol converted from a stabilizer better than the recurrence
protocol and the quantum privacy amplification protocol. The distillable
entanglement by the class of one-way protocols converted from stabilizer codes
for a certain class of states is equal to or greater than the achievable rate
of stabilizer codes over the channel corresponding to the distilled state, and
they can distill asymptotically more entanglement from a very noisy Werner
state than the hashing protocol.Comment: LaTeX2e, 18 pages, 1 figure. Version 4 added an example of two-way
protocols better than the recurrence protocol and the quantum privacy
amplification protocol. Version 2 added the quantum privacy amplification
protocol as an example converted from a stabilizer code, and corrected many
errors. Results unchanged from V
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