Unitary operations are expressed in the quantum circuit model as a finite sequence of elementary gates, such as controlled-not gates and single qubit gates. We prove that the simplified Toffoli gate by Margolus, which coincides with the Toffoli gate up to a single change of sign, cannot be realized with less than three controlled-not gates. If the circuit is implemented with three controlled-no...

This paper presents a lookup table based method for switch networks and logic gates implementation. The proposed approach is able to deliver optimal transistor networks for all Boolean functions up to four inputs. Results show a new transistor count lower bound for P-class and NPN-class for four inputs logic gates.

We address the problem of constructing quantum circuits to implement an arbitrary two-qubit quantum computation. We pursue circuits without ancilla qubits and as small a number of elementary quantum gates as possible. Our lower bound for worst-case optimal two-qubit circuits calls for at least 17 gates: 15 one-qubit rotations and 2 controlled-NOT ~CNOT! gates. We also constructively prove a wor...

Today, the use of CMOS technology for the manufacture of electronic ICs has faced many limitations. Many alternatives to CMOS technology are offered and made every day. Quantum-dot cellular automata (QCA) is one of the most widely used. QCA gates and circuits have many advantages including small size, low power consumption and high speed. On the other hand, using special digital gates called re...

Quantum cellular automata (QCA) enables performing arithmetic and logic operations at the molecular scale. This nanotechnology promises high device density, low power consumption and high computational power. Unlike the CMOS technology where the ON and OFF states of the transistors represent binary information, in QCA, data is represented by the charge configuration. The primary and basic devic...

We propose a theoretical protocol for preparing four-photon polarization entangled decoherence-free states, which are immune to the collective noise. With the assistance of the cross-Kerr nonlinearities, a two-photon spatial entanglement gate, two controlled-NOT gates, a four-photon polarization entanglement gate are inserted into the circuit, where X homodyne measurements are aptly applied. Co...

Two-phase dynamic FET !ogic (TDFL) gates are used in GaAs MESFET MSI circuits to implement very low power 4-b ripple carry adders and a variable modulus (2 to 31) prescaler. Operation of the adders is demonstrated at 500 MHz with an associated power dissipation of less than 1.0 mW and at 750 MHz with p d = 1.7 mW. The prescaler, which contains 166 TDFL gates and 79 static gates, i s shown to op...

It is known that every two-qubit unitary operation has Schmidt rank one, two or four, and the construction of three-qubit gates in terms remains an open problem. We explicitly construct from one to seven. turns out Toffoli Fredkin gate, respectively, have four. As application, we implement using quantum circuits CNOT local Hadamard flip gates. In particular, collective use three can generate a ...