3,924 research outputs found
Classification of three-body quantum halos
The different kinds of behaviour of three-body systems in the weak binding
limit are classified with specific attention to the transition from a true
three-body system to an effective two-body system. For weakly bound Borromean
systems approaching the limit of binding we show that the size-binding energy
relation is an almost universal function of the three s-wave scattering lengths
measured in units of a hyperradial scaling parameter defined as a mass weighted
average of two-body equivalent square well radii. We explain why three-body
halos follow this curve and why systems appearing above reveal two-body
substructures. Three-body quantum halos 2-3 times larger than the limit set by
zero hypermoment are possible
Bidirectional imperfect quantum teleportation with a single Bell state
We present a bidirectional modification of the standard one-qubit
teleportation protocol, where both Alice and Bob transfer noisy versions of
their qubit states to each other by using single Bell state and auxiliary
(trigger) qubits. Three schemes are considered: the first where the actions of
parties are governed by two independent quantum random triggers, the second
with single random trigger, and the third as a mixture of the first two. We
calculate the fidelities of teleportation for all schemes and find a condition
on correlation between trigger qubits in the mixed scheme which allows us to
overcome the classical fidelity boundary of 2/3. We apply the Choi-Jamiolkowski
isomorphism to the quantum channels obtained in order to investigate an
interplay between their ability to transfer the information,
entanglement-breaking property, and auxiliary classical communication needed to
form correlations between trigger qubits. The suggested scheme for
bidirectional teleportation can be realized by using current experimental
tools.Comment: 8 pages, 4 figures; published versio
Symmetric blind information reconciliation and hash-function-based verification for quantum key distribution
We consider an information reconciliation protocol for quantum key
distribution (QKD). In order to correct down the error rate, we suggest a
method, which is based on symmetric blind information reconciliation for the
low-density parity-check (LDPC) codes. We develop a subsequent verification
protocol with the use of -universal hash functions, which allows
verifying the identity between the keys with a certain probability.Comment: 4 pages; 1 figure; published versio
Teleportation in an indivisible quantum system
Teleportation protocol is conventionally treated as a method for quantum
state transfer between two spatially separated physical carriers. Recent
experimental progress in manipulation with high-dimensional quantum systems
opens a new framework for implementation of teleportation protocols. We show
that the one-qubit teleportation can be considered as a state transfer between
subspaces of the whole Hilbert space of an indivisible eight-dimensional
system. We explicitly show all corresponding operations and discuss an
alternative way of implementation of similar tasks.Comment: 4 pages, 1 figure, 1 tabl
Superfluidity of identical fermions in an optical lattice: atoms and polar molecules
In this work, we discuss the emergence of -wave superfluids of identical
fermions in 2D lattices. The optical lattice potential manifests itself in an
interplay between an increase in the density of states on the Fermi surface and
the modification of the fermion-fermion interaction (scattering) amplitude. The
density of states is enhanced due to an increase of the effective mass of
atoms. In deep lattices, for short-range interacting atoms, the scattering
amplitude is strongly reduced compared to free space due to a small overlap of
wavefunctions of fermions sitting in the neighboring lattice sites, which
suppresses the -wave superfluidity. However, we show that for a moderate
lattice depth there is still a possibility to create atomic -wave
superfluids with sizable transition temperatures. The situation is drastically
different for fermionic polar molecules. Being dressed with a microwave field,
they acquire a dipole-dipole attractive tail in the interaction potential.
Then, due to a long-range character of the dipole-dipole interaction, the
effect of the suppression of the scattering amplitude in 2D lattices is absent.
This leads to the emergence of a stable topological superfluid of
identical microwave-dressed polar molecules.Comment: 14 pages, 4 figures; prepared for proceedings of the IV International
Conference on Quantum Technologies (Moscow, July 12-16, 2017); the present
paper summarizes the results of our studies arXiv:1601.03026 and
arXiv:1701.0852
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