Research a key step towards quantum computers (Harvard Gazette)
By Peter Reuell, Harvard News Office
Harvard scientists have taken a critical step toward building a quantum computer — a device that could someday harness, for example, the intrinsic properties of subatomic particles such as electrons to perform calculations far faster than the most powerful supercomputers.
As described in a paper published April 13 in Science, researchers have, for the first time, demonstrated a system in which two semiconducting spin quantum bits, or qubits, interact with each other in a process known as entanglement. Without that entanglement, quantum computers simply can’t exist.
“Entanglement is an essential component of quantum computing — it’s what gives you the ability to do generalized, universal quantum computation,” said Amir Yacoby, professor of physics and of applied physics, who led the research. “Without this kind of entanglement, there’s no way to get anywhere in this field.”
Quantum computers rely on quantum mechanical properties of particles to store data and perform computations. Unlike the transistors used in digital computers, which encode data “bits” as either zero or one, qubits can hold both values simultaneously. In theory, that inherently parallel nature allows quantum computers to be vastly more powerful than traditional computers, which perform operations in sequence… [more]
A robust new architecture enables optimization for quantum-dot displays
Cambridge, Mass. – November 15, 2011 – By nestling quantum dots in an insulating egg-crate structure, researchers at the Harvard School of Engineering and Applied Sciences (SEAS) have demonstrated a robust new architecture for quantum-dot light-emitting devices (QD-LEDs).
Quantum dots are very tiny crystals that glow with bright, rich colors when stimulated by an electric current. QD-LEDs are expected to find applications in television and computer screens, general light sources, and lasers.
Previous work in the field had been complicated by organic molecules called ligands that dangle from the surface of the quantum dots. The ligands play an essential role in quantum dot formation, but they can cause functional problems later on.
Thanks to an inventive change in technique devised by the Harvard team, the once-troublesome ligands can now be used to build a more versatile QD-LED structure. The new single-layer design, described in the journal Advanced Materials, can withstand the use of chemical treatments to optimize the device’s performance for diverse applications….
Researchers control the rate of photon emission from luminescent imperfections in diamond
Cambridge, Mass. – October 9, 2011 – Engineers and physicists at Harvard have managed to capture light in tiny diamond pillars embedded in silver, releasing a stream of single photons at a controllable rate.
The advance represents a milestone on the road to quantum networks in which information can be encoded in spins of electrons and carried through a network via light, one photon at a time.
The finding was published in Nature Photonics, appearing online on October 9.
“We can make the emission of photons faster, which will allow us to do more processing per second—for example, more computations—in the future quantum network,” explains principal investigator Marko Lončar, Associate Professor of Electrical Engineering at the Harvard School of Engineering and Applied Sciences (SEAS)….