Abstract
We investigate the resources needed for secure teleportation of coherent states. We extend continuous variable teleportation to include quantum teleamplification protocols that allow nonunity classical gains and a preamplification or postattenuation of the coherent state. We show that, for arbitrary Gaussian protocols and a significant class of Gaussian resources, two-way steering is required to achieve a teleportation fidelity beyond the no-cloning threshold. This provides an operational connection between Gaussian steerability and secure teleportation. We present practical recipes suggesting that heralded noiseless preamplification may enable high-fidelity heralded teleportation, using minimally entangled yet steerable resources.
Highlights
What type of EPR entanglement is required for continuous variable (CV) quantum teleportation [14]? CV teleportation of a coherent state originally focused on a subset of entangled resource states, where the entanglement can be certified by the Tan-Duan criterion which treats Alice and Bob symmetrically [15,16,17]:
Once one allowed for local operations at Alice and Bob’s stations to optimise the protocol, it became clear that all two-mode Gaussian entangled states could be utilised for CV Quantum teleportation (QT) [19, 20] with fidelity F exceeding 1/2, which is the standard benchmark for input coherent states [21]
We present two simple protocols that are readily achievable experimentally and that together with the Braunstein and Kimble (BK) protocol allow, for any lossy two-mode squeezed state (TMSS) resource, quantum teleportation with a fidelity spanning the whole range within the Mari and Vitali (MV) bounds, Eq (6)
Summary
We conclude by suggesting a further application of EPR steering to enhance the fidelity. We show in the Supplemental Material that for the TMSS resource with the optimal choice of g (gopt = tanh(r)), we get F → 1. This is valid for all r > 0, it does not require significant entanglement of the teleportation resource.
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