Coherent manipulation of semiconductor quantum bits with terahertz radiation

Abstract

Quantum bits^1,2,3,4,5 (qubits) are the fundamental building blocks of quantum information processors, such as quantum computers⁶. A qubit comprises a pair of well characterized quantum states that can in principle be manipulated quickly compared to the time it takes them to decohere by coupling to their environment⁷. Much remains to be understood about the manipulation and decoherence of semiconductor qubits. Here we show that hydrogen-atom-like motional states of electrons bound to donor impurities in currently available semiconductors can serve as model qubits. We use intense pulses⁸ of terahertz radiation to induce coherent, damped Rabi oscillations^9,10 in the population of two low-lying states of donor impurities in GaAs^11,12,13. Our observations demonstrate that a quantum-confined extrinsic electron in a semiconductor can be coherently manipulated like an atomic electron, even while sharing space with ∼ 10⁵ atoms in its semiconductor host. We anticipate that this model system will be useful for measuring intrinsic decoherence processes, and for testing both simple and complex manipulations of semiconductor qubits.