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.
Highlights
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
We present an experimental demonstration of arbitrary single-qubit SU(2) quantum gate operations achieved at a terahertz clock speed
The clock speed of a CPU has reached 10 GHz, and in an attempt to further improve computational speeds, new types of computer architectures are under active investigation[3,4,5]
Summary
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. The second experiment demonstrates the phase-shift gate operation performed by the far-detuned pulse and measured with the ultrafast Ramsey interferometry (see Methods for details). When Q 5 [0, 0, p, p, p, 0], the probability change (red circles and line) is [0 R 0.5 R 1 R 0.5 R 0 R 0.5 R 0] This demonstration of time-fragmented Rabi rotations confirms that ultrafast quantum gates can operate at a speed of 1 THz. Qubits in quantum computation are the fundamental passive elements of the machine. The demonstrated scheme has performed single-qubit gates at an operational clock speed as high as 1 THz. The improvement of the operating speed benefits the computational power of a quantum computer by enabling a huge number of operations within a limited coherence time. The coherent control method could simplify otherwise complex optical implementation of a quantum circuit, replacing heterogeneous optical control sources by a temporally- and spectrally-programmed pulse sequence from a single ultrafast laser source
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