Phys. Rev. Lett. 114, 170504 (2015)
How can one detect entanglement between multiple optical paths sharing a single photon? We address this question by proposing a scalable protocol, which only uses local measurements where single photon detection is combined with small displacement operations. The resulting entanglement witness does not require postselection, nor assumptions about the photon number in each path. Furthermore, it guarantees that entanglement lies in a subspace with at most one photon per optical path and reveals genuinely multipartite entanglement.
E. G. Brow, W. Donnelly, A. Kempf, R. B. Mann, E. Martín-Martínez, and N. C. Menicucci
New Journal of Physics 16, 105020 (2014)
Entanglement farming is a protocol that involves successively sending pairs of “particle detectors” (such as atoms, ions, molecules, etc) transversely through an optical cavity. As pair after pair traverses the cavity, the field approaches a fixed-point state, where every pair of atoms emerges from the cavity in the same state, which is generically entangled. The fixed point is generally stable to small changes in the parameters.
Increasing Sensing Resolution with Error Correction
G. Arrad, Y. Vinkler, D. Aharonov, A. Retzker
Phys. Rev. Lett. 112, 150801 (2014);
Quantum Error Correction for Metrology
E. M. Kessler, I. Lovchinsky, A. O. Sushkov, M. D. Lukin
Phys. Rev. Lett. 112, 150802 (2014);
Improved Quantum Metrology Using Quantum Error Correction
W. Dür, M. Skotiniotis, F. Fröwis, B. Kraus
Phys. Rev. Lett. 112, 080801 (2014)
E. M. Kessler, P. Kómár, M. Bishof, L. Jiang, A. S. Sørensen, J. Ye, M. D. Lukin
Phys. Rev. Lett. 112, 190403 (2014)
The improvement of frequency standards using quantum resources, such as entanglement has been actively explored in recent years. The use of entangled resources, in principle, allows one to surpass the classical limit on precision. However, a characterization of the improvement obtainable by using entanglement requires a detailed investigation of the decoherence present in the system.
M. D. Vidrighin, G. Donati, M. G. Genoni, X.-M. Jin, W. S. Kolthammer, M. S. Kim, A. Datta, M. Barbieri, I. A. Walmsley
Nature Communications 5, 3532 (2014)
Phase estimation is one of the most studied quantum metrology situations, with wide-ranging practical applications. In many realistic situations, phase and phase diffusion may vary in time. Consequently, the accuracy of phase estimation may be affected by varying estimates of the magnitude of phase diffusion.
R. Demkowicz-Dobrzański, L. Maccone
Phys. Rev. Lett. 113, 250801 (2014)
Quantum metrology provides super-classical scaling in measurement precision by exploiting quantum effects. A crucial question in the field is to understand when entangled states lead to super-classical scaling.
J. Tura, R. Augusiak, A. B. Sainz, T. Vértesi, M. Lewenstein, and A. Acín
Science 344, 1256 (2014)
U. Vazirani, T. Vidick
Phys. Rev. Lett. 113, 140501 (2014)
D. W. Berry, A. M. Childs, R. Cleve, R. Kothari, R. D. Somma
Proceedings of the 46th ACM Symposium on Theory of Computing (STOC 2014), 283-292 (2014)
Simulation of quantum mechanical systems is a major potential application of quantum computers. Indeed, the problem of simulating Hamiltonian dynamics was the original motivation for the idea of quantum computation.
D. Aharonov, A. W. Harrow, Z. Landau, D. Nagaj, M. Szegedy, U. Vazirani
Proceedings of FOCS 2014, 246 (2014)