2,851 research outputs found
Storage and Retrieval of Thermal Light in Warm Atomic Vapor
We report slowed propagation and storage and retrieval of thermal light in
warm rubidium vapor using the effect of electromagnetically-induced
transparency (EIT). We first demonstrate slowed-propagation of the probe
thermal light beam through an EIT medium by measuring the second-order
correlation function of the light field using the Hanbury-BrownTwiss
interferometer. We also report an experimental study on the effect of the EIT
slow-light medium on the temporal coherence of thermal light. Finally, we
demonstrate the storage and retrieval of thermal light beam in the EIT medium.
The direct measurement of the photon number statistics of the retrieved light
field shows that the photon number statistics is preserved during the storage
and retrieval process.Comment: 4 pages, 4 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
Single-Copy Certification of Two-Qubit Gates without Entanglement
A quantum state transformation can be generally approximated by single- and
two-qubit gates. This, however, does not hold with noisy intermediate-scale
quantum technologies due to the errors appearing in the gate operations, where
errors of two-qubit gates such as controlled-NOT and SWAP operations are
dominated. In this work, we present a cost efficient single-copy certification
for a realization of a two-qubit gate in the presence of depolarization noise,
where it is aimed to identify if the realization is noise-free, or not. It is
shown that entangled resources such as entangled states and a joint measurement
are not necessary for the purpose, i.e., a noise-free two-qubit gate is not
needed to certify an implementation of a two-qubit gate. A proof-of-principle
demonstration is presented with photonic qubits.Comment: 8 pages. arXiv admin note: text overlap with arXiv:1812.0208
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