We demonstrate a new architecture for an optical entangling gate that is significantly simpler than previous realizations, using partially polarizing beam splitters so that only a single optical mode-matching condition is required. We demonstrate operation of a controlled-z gate in both continuous-wave and pulsed regimes of operation, fully characterizing it in each case using quantum process t...

A porphyrin-silicon nanowire (Si-NW) hybrid field-effect transistor is introduced. The hybrid device has separate electrical and optical gates surrounding the Si-NW channel. Porphyrin, a component of chlorophyll, is employed as an optical gate to modulate the potential of the Si-NW channel. Due to the independently formed hybrid gates, both optical and electrical excitation can effectively modu...

in this paper a novel all-optical logic nand, nor and xor gate based on nonlinear directional coupler theory is demonstrated. we use the identical structure which contains three waveguides, for designing these gates; the only difference however, is the power of inputs light beam. in other words, while a beam with 4 w/μm in power considered as logical one, the output is nand gate and if a beam w...

A breadth-first search method for determining optimal 3-qubit circuits composed of quantum NOT, CNOT, controlled-V and controlled-V+ (NCV) gates is introduced. Results are presented for simple gate count and for technology motivated cost metrics. The optimal NCV circuits are also compared to NCV circuits derived from optimal NOT, CNOT and Toffoli (NCT) gate circuits. The work presented here pro...

We establish theoretical bounds on qubit detuning for some of the previously proposed controlled-NOT !CNOT" logic gate implementations with weakly coupled Josephson phase qubits. It is found that in the twostep, #iSWAP-based case the value of the detuning during the entangling operations must not exceed 2g, where g is the characteristic coupling constant. In the single-step case we consider two...

Abstract. The SWAP gate has become an integral feature of quantum circuit architectures and is designed to permute the states of two qubits through the use of the well-known controlled-NOT gate. We consider the question of whether a two-qudit quantum circuit composed entirely from instances of the generalised controlled-NOT gate can be constructed to permute the states of two qudits. Arguing vi...

Building on the previous results of the Weyl chamber steering method, we demonstrate how to generate high-fidelity CNOT by direct application of certain, physically relevant Hamiltonians with fixed coupling constants containing Rabi terms. Such Hamiltonians are often used to describe two superconducting qubits driven by local rf-pulses. It is found that in order to achieve 100% fidelity in a sy...

While the question “how many CNOT gates are needed to simulate an arbitrary twoqubit operator” has been conclusively answered – three are necessary and sufficient – previous work on this topic assumes that one wants to simulate a given unitary operator up to global phase. However, in many practical cases additional degrees of freedom are allowed. For example, if the computation is to be followe...

We study the phenomenon of decoherence during the operation of one qubit transformation, controlled-not (CNOT) and controlled-controlled-not (CNOT) quantum gates in a quantum computer model formed by a linear chain of three nuclear spins system. We make this study with different type of environments, and we determine the associated decoherence time as a function of the dissipative parameter. We...

The reversible logic can be used in various research areas, e. g. quantum computation, cryptography and signal processing. In the paper we study reversible logic circuits with additional inputs, which consist of NOT, CNOT and C2NOT gates. We consider a set F (n, q) of all transformations Bn → Bn that can be realized by reversible circuits with (n+q) inputs. An analogue of Lupanov’s method for t...