4,921 research outputs found
Decomposition of the efficiency of the Chinese state-owned commercial banks at the provincial level
This study adopts a bank production function approach to the measurement of banking efficiency at the provincial level in the Chinese state-owned commercial banking sector from 1998 to 2003. Applying Data Envelopment Analysis and efficiency decomposition analysis, this paper has revealed a significant level of pure technical input inefficiency and, to a lesser extent, scale inefficiency across the provincial branches of all the banking groups. The study has also uncovered the extent of inefficiency in individual banking inputs and provincial branches. Finally, the provincial-level efficiency is further decomposed into within-banking-group and between-banking-group effects
Improving Einstein-Podolsky-Rosen Steering Inequalities with State Information
We discuss the relationship between entropic Einstein-Podolsky-Rosen
(EPR)-steering inequalities and their underlying uncertainty relations, along
with the hypothesis that improved uncertainty relations lead to tighter
EPR-steering inequalities. In particular, we discuss how the intrinsic
uncertainty in a mixed quantum state is used to improve existing uncertainty
relations and how this information affects one's ability to witness
EPR-steering. As an example, we consider the recent improvement (using a
quantum memory) to the entropic uncertainty relation between pairs of discrete
observables (Nat. Phys. 6, 659 (2010)) and show that a trivial substitution of
the tighter bound in the steering inequality leads to contradictions, due in
part to the fact that the improved bound depends explicitly on the state being
measured. By considering the assumptions that enter into the development of a
steering inequality, we derive correct steering inequalities from these
improved uncertainty relations and find that they are identical to ones already
developed (Phys. Rev. A, 87, 062103 (2013)). In addition, we consider how one
can use the information about the quantum state to improve our ability to
witness EPR-steering, and develop a new symmetric EPR-steering inequality as a
result.Comment: 6 page
Uncertainty Relation for Mutual Information
We postulate the existence of a universal uncertainty relation between the
quantum and classical mutual informations between pairs of quantum systems.
Specifically, we propose that the sum of the classical mutual information,
determined by two mutually unbiased pairs of observables, never exceeds the
quantum mutual information. We call this the complementary-quantum correlation
(CQC) relation and prove its validity for pure states, for states with one
maximally mixed subsystem, and for all states when one measurement is minimally
disturbing. We provide results of a Monte Carlo simulation suggesting the CQC
relation is generally valid. Importantly, we also show that the CQC relation
represents an improvement to an entropic uncertainty principle in the presence
of a quantum memory, and that it can be used to verify an achievable secret key
rate in the quantum one-time pad cryptographic protocol.Comment: 6 pages, 2 figure
Bounding the entanglement of N qubits with only four measurements
We introduce a new measure for the genuinely N-partite (all-party)
entanglement of N-qubit states using the trace distance metric, and find an
algebraic formula for the GHZ-diagonal states. We then use this formula to show
how the all-party entanglement of experimentally produced GHZ states of an
arbitrary number of qubits may be bounded with only four measurements
Experimental Violation of Two-Party Leggett-Garg Inequalities with Semi-weak Measurements
We generalize the derivation of Leggett-Garg inequalities to systematically
treat a larger class of experimental situations by allowing multi-particle
correlations, invasive detection, and ambiguous detector results. Furthermore,
we show how many such inequalities may be tested simultaneously with a single
setup. As a proof of principle, we violate several such two-particle
inequalities with data obtained from a polarization-entangled biphoton state
and a semi-weak polarization measurement based on Fresnel reflection. We also
point out a non- trivial connection between specific two-party Leggett-Garg
inequality violations and convex sums of strange weak values.Comment: 4 pages, 6 figure
Quantum Fully Homomorphic Encryption With Verification
Fully-homomorphic encryption (FHE) enables computation on encrypted data
while maintaining secrecy. Recent research has shown that such schemes exist
even for quantum computation. Given the numerous applications of classical FHE
(zero-knowledge proofs, secure two-party computation, obfuscation, etc.) it is
reasonable to hope that quantum FHE (or QFHE) will lead to many new results in
the quantum setting. However, a crucial ingredient in almost all applications
of FHE is circuit verification. Classically, verification is performed by
checking a transcript of the homomorphic computation. Quantumly, this strategy
is impossible due to no-cloning. This leads to an important open question: can
quantum computations be delegated and verified in a non-interactive manner? In
this work, we answer this question in the affirmative, by constructing a scheme
for QFHE with verification (vQFHE). Our scheme provides authenticated
encryption, and enables arbitrary polynomial-time quantum computations without
the need of interaction between client and server. Verification is almost
entirely classical; for computations that start and end with classical states,
it is completely classical. As a first application, we show how to construct
quantum one-time programs from classical one-time programs and vQFHE.Comment: 30 page
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