34,362 research outputs found
Signifying quantum benchmarks for qubit teleportation and secure communication using Einstein-Podolsky-Rosen steering inequalities
The demonstration of quantum teleportation of a photonic qubit from Alice to
Bob usually relies on data conditioned on detection at Bob's location. I show
that Bohm's Einstein-Podolsky-Rosen (EPR) paradox can be used to verify that
the quantum benchmark for qubit teleportation has been reached, without
postselection. This is possible for scenarios insensitive to losses at the
generation station, and with efficiencies of for the
teleportation process. The benchmark is obtained, if it is shown that Bob can
{}"steer" Alice's record of the qubit as stored by Charlie. EPR steering
inequalities involving measurement settings can also be used to confirm
quantum teleportation, for efficiencies , if one assumes trusted
detectors for Charlie and Alice. Using proofs of monogamy, I show that
two-setting EPR steering inequalities can signify secure teleportation of the
qubit state.Comment: 10 pages, 1 Figur
Macroscopic Local Realism Incompatible with Quantum Mechanics: Failure of Local Realism where Measurements give Macroscopic Uncertainties
We show that quantum mechanics predicts a contradiction with local hidden
variable theories for photon number measurements which have limited resolving
power, to the point of imposing an uncertainty in the photon number result
which is macroscopic in absolute terms. We show how this can be interpreted as
a failure of a new premise, macroscopic local realism.Comment: 9 pages 3 figure
Einstein-Podolsky-Rosen paradox and quantum steering in pulsed optomechanics
We describe how to generate an Einstein-Podolsky-Rosen (EPR) paradox between
a mesoscopic mechanical oscillator and an optical pulse. We find two types of
paradox, defined by whether it is the oscillator or the pulse that shows the
effect Schrodinger called "steering". Only the oscillator paradox addresses the
question of mesoscopic local reality for a massive system. In that case, EPR's
"elements of reality" are defined for the oscillator, and it is these elements
of reality that are falsified (if quantum mechanics is complete). For this sort
of paradox, we show that a thermal barrier exists, meaning that a threshold
level of pulse-oscillator interaction is required for a given thermal
occupation n_0 of the oscillator. We find there is no equivalent thermal
barrier for the entanglement of the pulse with the oscillator, nor for the EPR
paradox that addresses the local reality of the optical system. Finally, we
examine the possibility of an EPR paradox between two entangled oscillators.
Our work highlights the asymmetrical effect of thermal noise on quantum
nonlocality.Comment: 9 pages, 7 figure
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