Optical Pulse Control of Electron and Nuclear Spins in Quantum Dots
Abstract
Quantum information has the potential to revolutionize secure communications and computation, both important to the Department of Defense. The unique properties of quantum bits (qubits, units of quantum information) and the phenomenon of entanglement (non-local, non-classical correlation) prevent eavesdropping over quantum communication channels and enable the solving of problems that grow exponentially difficult with classical computation, including decryption of codes with long encryption keys. Electron spins in quantum dots (QDs) are being widely investigated as qubits for storage and processing of quantum information, with the two different directions of the spin, up or down, forming the two states of the qubit. NRL is a leader in developing semiconductor QDs for quantum information, both in materials development and in probing the quantum nature of these nanometer-scale structures. Controlling the spin in these QDs, including increasing the spin coherence time, is a key area of NRL research. The electron spin coherence time in a QD, or lifetime of the qubit, can be at least microseconds, but the coherence is easily masked by the many (10,000-100,000) randomly oriented nuclear spins that also exist in the QD. The net nuclear spin acts as a temporally fluctuating magnetic field that randomizes the phase of the electron spin qubit. We use a train of picosecond laser pulses at wavelengths near an electronic QD transition to manipulate the electron spin polarization and thereby control the nuclear spin polarization. This technique can be used to extend the electron spin coherence time in QDs, making this system more attractive for quantum information applications.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2009
- Accession Number
- ADA525026
Entities
People
- A. Bracker
- Andrew R. Shabaev
- S. Carter
- S. Economou
- T. Kennedy
- T. Reinecke
Organizations
- United States Naval Research Laboratory