Fidelity Of Operations Research Articles

Quantum gates with neutral atoms: Controlling collisional interactions in time-dependent traps

We theoretically study specific schemes for performing a fundamental two-qubit quantum gate via controlled atomic collisions by switching microscopic potentials. In particular we calculate the fidelity of a gate operation for a configuration where a potential barrier between two atoms is instantaneously removed and restored after a certain time. Possible implementations could be based on microtraps created by magnetic and electric fields, or potentials induced by laser light.

Optimal manipulations with qubits: Universal-NOT gate

Quantum information processing is usually associated with a specific computational basis. Nevertheless, for a deeper understanding of the fundamental principles of quantum computing, it is essential to investigate what is the fidelity of universal operations that are basis independent; i.e., the task is to perform optimally a specific operation on a qubit or a quantum register that is in an unknown state. In this paper we introduce the universal-NOT gate that takes as an input a qubit in an arbitrary state $|\ensuremath{\Psi}〉$ and generates an output that is as close as possible to the orthogonal state $|{\ensuremath{\Psi}}^{\ensuremath{\perp}}〉.$

Editorial

We demonstrate controlled-NOT (CNOT) operation of a silicon nitride photonic integrated circuit using path-entangled photon pairs from a silicon-photonic integrated circuit as logical inputs. The CNOT gate is constructed by combining several silicon-nitride Mach–Zehnder interferometers for a linear-optical quantum gate. We package each of the two photonic circuits with electrical wire bonding and optical fiber bonding for stable measurement. The logical-basis fidelity of CNOT operation is measured better than 81% for the fully packaged photonic circuits.