Ultrafast Ramsey interferometry to implement cold atomic qubit gates

Abstract

Quantum computing is based on unitary operations in a two-level quantum system, a qubit, as the fundamental building block, and the ability to perform qubit operations in an amount of time that is considerably shorter than the coherence time is an essential requirement for quantum computation. Here, we present an experimental demonstration of arbitrary single-qubit SU(2) quantum gate operations achieved at a terahertz clock speed. Implemented by coherent control methods of tailored ultrafast laser interaction with cold rubidium atomic qubits, Bloch vector manipulation about all three rotational axes was successfully demonstrated. The dynamic evolution of the qubits was successfully measured by devised femtosecond Ramsey interferometry. We anticipate this demonstration to be a starting point to process quantum algorithm in a simplified manner by a programmed sequence of femtosecond laser pulses.

Coherent quantum phase slip in two-component bosonic atomtronic circuits

“…Therefore, this overlap allows the coupling to occur locally, point to point, in the whole bulk of the condensate (long Josephson junction). With the aim of engineering a qubit we will select vortex states as the basis of an effective two-level system that is able to perform qubit operations [39]. The coherent coupling transfers vortices between both components in the absence of population imbalance, and the nonlinear system exhibits Rabi oscillations.…”

Berry-phase gates for fast and robust control of atomic clock states

“…2(a)]. Fast optical control of atomic and ion systems has been studied before through direct or Raman excitations [21][22][23], which we borrowed in the present work to implement adiabatic operations for geometric phases. Laser pulses were produced by a femtosecond Ti:sapphire amplifier system operated at a 1-kHz repetition rate (carrier frequency 377.1 THz, bandwidth 3.8 THz), which were resonant to the D 1 transition.…”

Subpicosecond X rotations of atomic clock states

“…Experimental investigation of the subpicosecond X rotation of the atomic clock states was performed in a setup described in our early works [25][26][27]. The setup composed of a magneto-optical trap (MOT) [28] for cold rubidium atoms ( 87 Rb) and a femtosecond laser amplifier [29].…”