Quantum information: Are we nearly there yet?

Doyeol Ahn, Sung Woo Hwang

We found that the Wigner rotation of a particle with spin 1/2, which is unitary in Minkowski spacetime, becomes non-unitary as the particle is falling onto the black hole. This implies that, from the quantum information processing point of view, any quantum information encoded in spins will be dissipated near the black hole. The gravitational field around the black hole thus acts like a dissipative quantum channel, especially the bit flip channel.

Vlatko Vedral

Gregg S. Jaeger

Shai Tsesses, Amit Kam, Yigal Ilin +11 more

We encode quantum information on photons confined to surface using a new degree-of-freedom unique to the near-field regime – Total angular momentum. We observe photon-pair non-classical correlations on-chip, as well as single-photon polarization-mode entanglement in free-space.

Thomas Durt

Mark Braverman, Ankit Garg, Young Kun Ko +2 more

We prove a near optimal round-communication tradeoff for the two-party quantum communication complexity of disjointness. For protocols with r rounds, we prove a lower bound of Omega(n/r) on the communication required for computing disjointness of input size n, which is optimal up to logarithmic factors. The previous best lower bound was Omega(n/r̂2) due to Jain, Radhakrishnan and Sen. Along the way, we develop several tools for quantum information complexity, one of which is a lower bound for quantum information complexity in terms of the generalized discrepancy method. As a corollary, we get that the quantum communication complexity of any boolean function f is at most 2 ̂O(QIC(f)), where QIC(f) is the prior-free quantum information complexity of f (with error 1/3).