11,792 research outputs found
Mode-Dependent Loss Model for Multimode Photon-Subtracted States
Multimode photon-subtraction provides an experimentally feasible option to
construct large non-Gaussian quantum states in continuous-variable quantum
optics. The non-Gaussian features of the state can lead towards the more exotic
aspects of quantum theory, such as negativity of the Wigner function. However,
the pay-off for states with such delicate quantum properties is their
sensitivity to decoherence. In this paper, we present a general model that
treats the most important source of decoherence in a purely optical setting:
losses. We use the framework of open quantum systems and master equations to
describe losses in n-photon-subtracted multimode states, where each photon can
be subtracted in an arbitrary mode. As a main result, we find that
mode-dependent losses and photon-subtraction generally do not commute. In
particular, the losses do not only reduce the purity of the state, they also
change the modal structure of its non-Gaussian features. We then conduct a
detailed study of single-photon subtraction from a multimode Gaussian state,
which is a setting that lies within the reach of present-day experiments.Comment: 14 pages, 8 figure
Reversing the Weak Quantum Measurement for a Photonic Qubit
We demonstrate the conditional reversal of a weak (partial-collapse) quantum
measurement on a photonic qubit. The weak quantum measurement causes a
nonunitary transformation of a qubit which is subsequently reversed to the
original state after a successful reversing operation. Both the weak
measurement and the reversal operation are implemented linear optically. The
state recovery fidelity, determined by quantum process tomography, is shown to
be over 94% for partial-collapse strength up to 0.9. We also experimentally
study information gain due to the weak measurement and discuss the role of the
reversing operation as an information erasure
The Korean case study : past experience and new trends in training policies
Korea's skills development strategy has been highlighted as one of the key driving forces of the country's economic development. This paper examines the main features and evolution of this strategy from the 1960s to the present. In particular, it discusses how the skills development policies have contributed to economic development and poverty reduction. The findings in the paper highlight a set of important lessons for the design and implementation of skills development policies, which could be useful for other developing countries.Education For All,Primary Education,Access&Equity in Basic Education,Population Policies,Labor Markets
Experimental verification of the commutation relation for Pauli spin operators using single-photon quantum interference
We report experimental verification of the commutation relation for Pauli
spin operators using quantum interference of the single-photon polarization
state. By superposing the quantum operations and on a single-photon polarization state, we have experimentally
implemented the commutator, , and the anticommutator,
, and have demonstrated the relative phase factor
of between and operations. The
experimental quantum operation corresponding to the commutator, , showed process fidelity of 0.94 compared to the ideal
operation and is determined to be .Comment: 4pages, 3 figure
Realizing Physical Approximation of the Partial Transpose
The partial transpose by which a subsystem's quantum state is solely
transposed is of unique importance in quantum information processing from both
fundamental and practical point of view. In this work, we present a practical
scheme to realize a physical approximation to the partial transpose using local
measurements on individual quantum systems and classical communication. We then
report its linear optical realization and show that the scheme works with no
dependence on local basis of given quantum states. A proof-of-principle
demonstration of entanglement detection using the physical approximation of the
partial transpose is also reported.Comment: 5 pages with appendix, 3 figure
Experimental Implementation of the Universal Transpose Operation
The universal transpose of quantum states is an anti-unitary transformation
that is not allowed in quantum theory. In this work, we investigate
approximating the universal transpose of quantum states of two-level systems
(qubits) using the method known as the structural physical approximation to
positive maps. We also report its experimental implementation in linear optics.
The scheme is optimal in that the maximal fidelity is attained and also
practical as measurement and preparation of quantum states that are
experimentally feasible within current technologies are solely applied.Comment: 4 pages, 4 figure
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