Quantum Dots: Ultrafast Control

Principal Investigator: Dr. Samuel G. Carter, sam.carter@nrl.navy.mil

As part of an effort to develop solid state implementations for quantum information, ultrafast optical pulse techniques are being used to coherently control the quantum state of electron spins in InAs quantum dots. Optical pulses are used to polarize the spins and to perform operations on the spin states, with the desired operations achieved through pulse detuning from the appropriate resonance(s) and the pulse bandwidth. Greater flexibility in this control is gained by using two pulsed lasers with different wavelengths. This ultrafast two-color technique has been used to achieve several goals to advance this system for quantum information:

1. Control of the electron spin orientation and the spatial extent of its wavefunction through excited state transitions
2. Stabilizing the nuclear spin environment in order to improve electron spin coherence
3. Single-qubit and two-qubit gates on a system of two spin qubits in separate quantum dots.

2011

• Ultrafast optical control of entanglement between two quantum dot spins, Nature Physics Vol 7 pp 223-229 (2011).
• Controlling the nuclear polarization in quantum dots using optical pulse shape, Phys. Rev. B. 83, 115325 (2011).

2010

• Electronic spin polarization and detection in InAs quantum dots through p-shell trions, Phys. Rev. B. 81, 045305 (2010).

2009

• Directing Nuclear Spin Flips in InAs Quantum Dots Using Detuned Optical Pulse Trains, Phys. Rev. Lett. 102, 167403 (2009).