378 research outputs found
Demonstration of Einstein-Podolsky-Rosen Steering Using Hybrid Continuous- and Discrete-Variable Entanglement of Light
Einstein-Podolsky-Rosen steering is known to be a key resource for one-sided
device-independent quantum information protocols. Here we demonstrate steering
using hybrid entanglement between continuous- and discrete-variable optical
qubits. To this end, we report on suitable steering inequalities and detail the
implementation and requirements for this demonstration. Steering is
experimentally certified by observing a violation by more than 5 standard
deviations. Our results illustrate the potential of optical hybrid entanglement
for applications in heterogeneous quantum networks that would interconnect
disparate physical platforms and encodings
All-Versus-Nothing Proof of Einstein-Podolsky-Rosen Steering
Einstein-Podolsky-Rosen steering is a form of quantum nonlocality
intermediate between entanglement and Bell nonlocality. Although Schr\"odinger
already mooted the idea in 1935, steering still defies a complete
understanding. In analogy to "all-versus-nothing" proofs of Bell nonlocality,
here we present a proof of steering without inequalities rendering the
detection of correlations leading to a violation of steering inequalities
unnecessary. We show that, given any two-qubit entangled state, the existence
of certain projective measurement by Alice so that Bob's normalized conditional
states can be regarded as two different pure states provides a criterion for
Alice-to-Bob steerability. A steering inequality equivalent to the
all-versus-nothing proof is also obtained. Our result clearly demonstrates that
there exist many quantum states which do not violate any previously known
steering inequality but are indeed steerable. Our method offers advantages over
the existing methods for experimentally testing steerability, and sheds new
light on the asymmetric steering problem.Comment: 7 pages, 2 figures. Accepted in Sci. Re
On the pure state outcomes of Einstein-Podolsky-Rosen steering
In the Einstein--Podolsky--Rosen experiment, when Alice makes a measurement
on her part of a bipartite system, Bob's part is collapsed to, or steered to, a
specific ensemble. Moreover, by reading her measurement outcome, Alice can
specify which state in the ensemble Bob's system is steered to and with which
probability. The possible states that Alice can steer Bob's system to are
called steered states. In this work, we study the subset of steered states
which are pure after normalisation. We illustrate that these pure steered
states, if they exist, often carry interesting information about the shared
bipartite state. This information content becomes particularly clear when we
study the purification of the shared state. Some applications are discussed.
These include a generalisation of the fundamental lemma in the so-called
`all-versus-nothing proof of steerability' for systems of arbitrary dimension.Comment: 7 pages, 0 figures; corrected typos and terminolog
Several Trade off Features of Quantum Steering in Distributed Scenario
In the present work, we address the question of how bipartite steering
violation takes place among multi-partite systems (where each sub-system have
Hilbert space dimension restricted to two) based on the maximal violations of
the bipartite steering inequality of the reduced pairwise qubit systems. We
have derived a trade-off relation which is satisfied by those pairwise
bipartite maximal steering violations, which physically can be understood as
providing restrictions on the distribution of steering among subsystems. For a
three-qubit system, it is impossible that all pairs of qubits violate the
steering inequality, and once a pair of qubits violates the steering inequality
maximally, the other two pairs of qubits must both obey the steering
inequality. We also present a complementarity relation between genuine
entanglement present in a tripartite state and maximum bipartite steering
violation by its reduced states.Comment: Close to published versio
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