Abstract
Extremely fast qubit controls can greatly reduce the calculation time in quantum computation, and potentially resolve the finite-time decoherence issues in many physical systems. Here, we propose and experimentally demonstrate pico-second time-scale controls of atomic clock state qubits, using Berry-phase gates implemented with a pair of chirped laser pulses. While conventional methods of microwave or Raman transitions do not allow atomic qubit controls within a time faster than the hyperfine free evolution period, our approach of ultrafast Berry-phase gates accomplishes fast clock-state operations. We also achieves operational robustness against laser parametric noises, since geometric phases are determined by adiabatic evolution pathway only, without being affected by any dynamic details. The experimental implementation is conducted with two linearly polarized, chirped ultrafast optical pulses, interacting with five single rubidium atoms in an array of optical tweezer dipole traps, to demonstrate the proposed ultrafast clock-state gates and their operational robustness.
Highlights
The Berry phase is one of the hallmarks of quantum mechanics, dealing with the geometric phase, gained by a quantum wave function subjected to an adiabatic process, which can remain nonzero even after a cyclic evolution in which the more familiar dynamic phase disappears [1]
We propose and experimentally demonstrate a fast Berry-phase gate, which is implemented by picosecondtimescale optical pulses to make the qubit system of atomic clock states adiabatically evolve on a closed loop
The time evolution of a qubit system |ψ = α|0 + β|1 driven by the time-varying field of the Hamiltonian HI (t ) from ti to t f is written in the bare basis as
Summary
The Berry phase is one of the hallmarks of quantum mechanics, dealing with the geometric phase, gained by a quantum wave function subjected to an adiabatic process, which can remain nonzero even after a cyclic evolution in which the more familiar dynamic phase disappears [1]. It appears ubiquitously in numerous physical phenomena including the Aharonov-Bohm effect, the quantum Hall effect, and neutron interferometry, to list a few [1,2,3].
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