104 research outputs found
The Entanglement Level and the Detection of Quantum Data Transfer Correctness in Short Qutrit Spin Chains
The quantum entanglement is an important feature of many protocols in the
field of quantum computing. In this paper we evaluate a level of entanglement
in short qutrit chains. This evaluation is carried out with use of the CCNR
criterion and the concurrence measure. We also present some explicit formulae
describing the values of CCNR criterion and concurrence for exemplary short
spin chains. Utilizing the obtained results, we indicate that analyzing the
level of entanglement allows to detect the noise or deviation in the transfer
process, in comparison to the perfect transfer where only operation realizing
transfer is present.Comment: 15 pages, 9 figures, small typos fi
Economical (k,m)-threshold controlled quantum teleportation
We study a (k,m)-threshold controlling scheme for controlled quantum
teleportation. A standard polynomial coding over GF(p) with prime p > m-1 needs
to distribute a d-dimensional qudit with d >= p to each controller for this
purpose. We propose a scheme using m qubits (two-dimensional qudits) for the
controllers' portion, following a discussion on the benefit of a quantum
control in comparison to a classical control of a quantum teleportation.Comment: 11 pages, 2 figures, v2: minor revision, discussions improved, an
equation corrected in procedure (A) of section 4.3, v3: major revision,
protocols extended, citations added, v4: minor grammatical revision, v5:
minor revision, discussions extende
Quantum Algorithm Implementations for Beginners
As quantum computers become available to the general public, the need has
arisen to train a cohort of quantum programmers, many of whom have been
developing classical computer programs for most of their careers. While
currently available quantum computers have less than 100 qubits, quantum
computing hardware is widely expected to grow in terms of qubit count, quality,
and connectivity. This review aims to explain the principles of quantum
programming, which are quite different from classical programming, with
straightforward algebra that makes understanding of the underlying fascinating
quantum mechanical principles optional. We give an introduction to quantum
computing algorithms and their implementation on real quantum hardware. We
survey 20 different quantum algorithms, attempting to describe each in a
succinct and self-contained fashion. We show how these algorithms can be
implemented on IBM's quantum computer, and in each case, we discuss the results
of the implementation with respect to differences between the simulator and the
actual hardware runs. This article introduces computer scientists, physicists,
and engineers to quantum algorithms and provides a blueprint for their
implementations
Generation of Photonic Matrix Product States with a Rydberg-Blockaded Atomic Array
In this work, we show how one can deterministically generate photonic matrix
product states with high bond and physical dimensions with an atomic array if
one has access to a Rydberg-blockade mechanism. We develop both a quantum gate
and an optimal control approach to universally control the system and analyze
the photon retrieval efficiency of atomic arrays. Comprehensive modeling of the
system shows that our scheme is capable of generating a large number of
entangled photons. We further develop a multi-port photon emission approach
that can efficiently distribute entangled photons into free space in several
directions, which can become a useful tool in future quantum networks.Comment: 21 pages, 12 figure
Quantum Multiplexing with the Orbital Angular Momentum of light
The orbital angular momentum, OAM, of photons offers a suitable support to
carry the quantum data of multiple users. We present two novel optical setups
that send the information of n quantum communication parties through the same
free-space optical link. Those qubits can be sent simultaneously and share
path, wavelength and polarization without interference, increasing the
communication capacity of the system. The first solution, a qubit combiner,
merges n channels into the same link, which transmits n independent photons.
The second solution, the OAM multiplexer, uses CNOT gates to transfer the
information of n optical channels to a single photon. Additional applications
of the multiplexer circuits, such as quantum arithmetic, as well as connections
to OAM sorting are discussed
Collective Operations Can Exponentially Enhance Quantum State Verification
Maximally entangled states are a key resource in many quantum communication
and computation tasks, and their certification is a crucial element to
guarantee the desired functionality. We introduce collective strategies for the
efficient, local verification of ensembles of Bell pairs that make use of an
initial information and noise transfer to few copies prior to their
measurement. In this way the number of entangled pairs that need to be measured
and hence destroyed is significantly reduced as compared to previous, even
optimal, approaches that operate on individual copies. Moreover the remaining
states are directly certified. We show that our tools can be extended to other
problems and larger classes of multipartite states.Comment: 5 pages, 2 figure
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