Gaussification and entanglement distillation of continuous-variable systems: a unifying picture.

@article{Campbell2012GaussificationAE,
  title={Gaussification and entanglement distillation of continuous-variable systems: a unifying picture.},
  author={Earl T. Campbell and Jens Eisert},
  journal={Physical review letters},
  year={2012},
  volume={108 2},
  pages={
          020501
        }
}
Distillation of entanglement using only Gaussian operations is an important primitive in quantum communication, quantum repeater architectures, and distributed quantum computing. Existing distillation protocols for continuous degrees of freedom are only known to converge to a Gaussian state when measurements yield precisely the vacuum outcome. In sharp contrast, non-Gaussian states can be deterministically converted into Gaussian states while preserving their second moments, albeit by usually… 

Figures from this paper

Continuous-variable entanglement distillation by cascaded photon replacement
We study the entanglement distillation in continuous variable systems when a photon replacement protocol is employed. A cascaded protocol is studied and we find that the resultant entanglement
Efficient entanglement distillation without quantum memory
TLDR
The theory for an efficient iterative entanglement distillation protocol without quantum memories is presented and a proof-of-principle experimental demonstration is provided, which is particularly promising for enhancing continuous-variable quantum key distribution.
Roles of thermal noise and detector efficiency in distillation of continuous variable entanglement state
We address the degradation of continuous variable (CV) entanglement distillation in the presence of thermal environment and nonunity detecting efficiency. We explore the logarithmic negativity as a
Repeaters for continuous-variable quantum communication
TLDR
A design for continuous-variable quantum repeaters that can distribute entangled and pure two-mode squeezed states over arbitrarily long distances with a success probability that scales only polynomially with distance is presented.
Multi-step two-copy distillation of squeezed states via two photon subtraction
Squeezed states of light have been improving the sensitivity of gravitational-wave observatories and are nonclassical resources of quantum cryptography and envisioned photonic quantum computers. The
Rate limits in quantum networks with lossy repeaters
Riccardo Laurenza,1 Nathan Walk,1, 2 Jens Eisert,1, 3, 4 and Stefano Pirandola5 Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, 14195 Berlin, Germany Toshiba Research Europe
Adjonction cohérente itérative de photons pour la génération d'états quantiques mésoscopiques du champ électromagnétique
Cette these porte sur la generation d'etats quantiques mesoscopiques arbitraires de la lumiere par l'utilisation iteree d'un protocole elementaire simple, base sur un procede d'adjonction coherente
Entanglement enhancement in multimode integrated circuits
The faithful distribution of entanglement in continuous variable systems is essential to many quantum information protocols. As such, entanglement distillation and enhancement schemes are a

References

SHOWING 1-10 OF 63 REFERENCES
Gaussian transformations and distillation of entangled Gaussian states.
We prove that it is impossible to distill more entanglement from a single copy of a two-mode bipartite entangled Gaussian state via local Gaussian operations and classical communication. More
Distilling Gaussian states with Gaussian operations is impossible.
We show that no distillation protocol for Gaussian quantum states exists that relies on (i) arbitrary local unitary operations that preserve the Gaussian character of the state and (ii) homodyne
Distillation and purification of symmetric entangled Gaussian states
We propose an entanglement distillation and purification scheme for symmetric two-mode entangled Gaussian states that allows to asymptotically extract a pure entangled Gaussian state from any input
Entanglement distillation from Gaussian input states
TLDR
This work demonstrates, for the first time, such distillation from Gaussian input states, realized by the implementation of non-Gaussian operations, resulting in a large gain in entanglement.
Quantum repeaters with entangled coherent states
Entangled coherent states can be prepared remotely by subtracting non-locally a single photon from two quantum superpositions of coherent states, the so-called "Schroedinger's cat" state. Such
Extremality of Gaussian quantum states.
TLDR
It is proved that for every given covariance matrix the distillable secret key rate and the entanglement, if measured appropriately, are minimized by Gaussian states, implying that Gaussian encodings are optimal for the transmission of classical information through bosonic channels, if the capacity is additive.
Quantum repeaters based on atomic ensembles and linear optics
TLDR
The theoretical and experimental status quo of this very active field of quantum repeater protocols is reviewed, and the potentials of different approaches are compared quantitatively, with a focus on the most immediate goal of outperforming the direct transmission of photons.
Quantum repeaters based on entanglement purification
TLDR
A scheme is presented that allows entanglement purification over arbitrary long channels and tolerates errors on the percent level and requires a polynomial overhead in time, and an overhead in local resources that grows only logarithmically with the length of the channel.
Limitations of quantum computing with Gaussian cluster states
TLDR
It is demonstrated that even under arbitrary non-Gaussian local measurements, slabs of Gaussian cluster states of a finite width cannot carry logical quantum information, even if sophisticated encodings of qubits in continuous-variable systems are allowed for.
...
...