Implementation of quantum logic gates using polar molecules in pendular states

Abstract

We present a systematic approach to implementation of basic quantum logic gates operating on polar molecules in pendular states as qubits for a quantum computer. A static electric field prevents quenching of the dipole moments by rotation, thereby creating the pendular states; also, the field gradient enables distinguishing among qubit sites. Multi-target optimal control theory is used as a means of optimizing the initial-to-target transition probability via a laser field. We give detailed calculations for the SrO molecule, a favorite candidate for proposed quantum computers. Our simulation results indicate that NOT, Hadamard and CNOT gates can be realized with high fidelity, as high as 0.985, for such pendular qubit states.

Quantum Computation using Arrays of N Polar Molecules in Pendular States

“…[22,24] We studied entanglement measured by pairwise concurrence as af unction of molecular dipole moment,r otational constant, strengtho f externalf ield and dipole-dipole coupling. [22,24] We studied entanglement measured by pairwise concurrence as af unction of molecular dipole moment,r otational constant, strengtho f externalf ield and dipole-dipole coupling.…”

“…[22,24] We studied entanglement measured by pairwise concurrence as af unction of molecular dipole moment,r otational constant, strengtho f externalf ield and dipole-dipole coupling. [24] Here, we extendthe system from two to N qubits and examine the feasibility of quantum computation with 1-dimensional and 2-dimensional arrays of trapped dipolesi np endular states. [22] For ag iven frequency shift, Dw,w en umerically implemented NOT,H adamard and CNOT gates on two qubits encoded in pendular states of polar molecules.…”

Simulation of the elementary evolution operator with the motional states of an ion in an anharmonic trap

“…As predicted by Feynman, 3 quantum computers could be used as quantum simulators to solve stationary [4][5][6][7][8][9] or non stationary 10-13 quantum problems by simulating them with a controllable experimental setup which allows one to reproduce the dynamics of a given Hamiltonian. Several physical supports have been proposed to encode qubits: 14 photons, 15 spin states using nuclear magnetic resonance (NMR) technology, 16 quantum dots, 17 atoms, 18 molecular rovibrational levels of polyatomic or diatomic molecules, ultracold polar molecules, [48][49][50][51][52][53][54][55][56][57] or a juxtaposition of different types of systems. 58 In the current work, we focus on trapped ions [59][60][61][62][63][64] which remain one of the most attractive candidates due to the long coherence time scales and the possibility of exploiting the strong Coulomb interaction.…”

Quantum gates in hyperfine levels of ultracold alkali dimers by revisiting constrained-phase optimal control design

“…Ultracold polar molecules which can interact via dipole-dipole interaction are particularly interesting to create entanglement between neighboring molecules and to open the way toward qubit networks. [41][42][43][44][45][46][47][48] Alkali dimers also possess a rich spin structure because both nuclei have a nonzero spin. The spin interactions and the coupling with the overall rotation lead to hyperfine levels which can be further manipulated in magnetic or electric fields.…”

“…It seems intuitive to use the same quantity but it is not always the case in many previous applications. 33,38,44,48,54,55 It has been discussed early that realizing a gate transformation by an optimal field requires a careful choice of the performance measure. 56,57 The average transition probability for each computational basis state is not sufficient because the laser pulse is not able to drive any superposed state as it must do.…”