Some Examples of Post-Measurement Nonlocal Gates

Characterization of nonlocal gates

A nonlocal unitary transformation of two-qubits occurs when some Hamiltonian interaction couples them. Here we characterize the amount, as measured by time, of interaction required to perform two-qubit gates, when also arbitrarily fast, local unitary transformations can be applied on each qubit. The minimal required time of interaction, or interaction cost, defines an operational notion of the ...

Interaction cost of nonlocal gates.

We introduce the interaction cost of a nonlocal gate as the minimal time of interaction required to perform the gate when assisting the process with fast local unitaries. This cost, of interest both in the areas of quantum control and quantum information, depends on the specific interaction, and allows one to compare in an operationally meaningful manner any two nonlocal gates. In the case of a...

Instantaneous Measurement of Nonlocal Variables

We ask the question: is it possible to measure nonlocal properties of a state instantaneously? Relativistic causality restricts how this can be done, but we show here, for the bipartite two dimensional case, that every nonlocal variable of the system can be measured instantaneously. A necessary condition for a general nonlocal measurement on a bipartite system is presented. This essay was writt...

Instantaneous measurement of nonlocal variables.

It is shown, under the assumption of the possibility to perform an arbitrary local operation, that all nonlocal variables related to two or more separate sites can be measured instantaneously, except for a finite time required for bringing to one location the classical records from these sites which yield the result of the measurement. It is a verification measurement: it yields reliably the ei...

Representations : Some Examples