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Quantum random access memory.
An architecture that exponentially reduces the requirements for a memory call: O(logN) switches need be thrown instead of the N used in conventional RAM designs, which yields a more robust QRAM algorithm, as it in general requires entanglement among exponentially less gates, and leads to an exponential decrease in the power needed for addressing.
Quantum-Enhanced Measurements: Beating the Standard Quantum Limit
This work has shown that conventional bounds to the precision of measurements such as the shot noise limit or the standard quantum limit are not as fundamental as the Heisenberg limits and can be beaten using quantum strategies that employ “quantum tricks” such as squeezing and entanglement.
Advances in quantum metrology
The statistical error in any estimation can be reduced by repeating the measurement and averaging the results. The central limit theorem implies that the reduction is proportional to the square root
Quantum metrology.
It is proved that the typical quantum precision enhancement is of the order of the square root of the number of times the system is sampled, and it is pointed out the different strategies that permit one to attain this bound.
Quantum illumination with Gaussian states.
By making the optimum joint measurement on the light received from the target region together with the retained spontaneous parametric down-conversion idler beam, the quantum-illumination system realizes a 6 dB advantage in the error-probability exponent over the optimum reception coherent-state system.
Architectures for a quantum random access memory
Two different RAM architectures are analyzed and some proof-of-principle implementations are proposed which show that in principle only O(n) two-qubit physical interactions need take place during each qRAM call, which could give rise to the construction of large qRAMs that could operate without the need for extensive quantum error correction.
Classical capacity of the lossy bosonic channel: the exact solution.
The classical capacity of the lossy bosonic channel is calculated exactly. It is shown that its Holevo information is not superadditive, and that a coherent-state encoding achieves capacity. The
Stronger uncertainty relations for all incompatible observables.
Two stronger uncertainty relations are given, relating to the sum of variances, whose lower bound is guaranteed to be nontrivial whenever the two observables are incompatible on the state of the system.
Using entanglement against noise in quantum metrology.
It is proved that entangled strategies can have higher precision than unentangled ones and that the addition of passive external ancillas can also increase the precision.
Quantum Time
We give a consistent quantum description of time, based on Page and Wootters’ and on Aharonov and Kaufherr’s conditional probabilities mechanism, that overcomes the criticisms that were raised