Quantum computers’ inherent computational advantage comes from their fundamental computational unit, the quantum bit termed as the qubit. Unlike a digital bit in a classical computer, which can take the form of either 0 or 1, a qubit can be both zero and one simultaneously, throwing open the door to vastly more powerful computation. Though a usable computer based on qubits remains still allusive, investigators and researchers continue to make efforts toward their realization.
Research teams from University College London, the University of Utah and Florida State University in Tallahassee show one more step toward the development of a quantum computer. The team showed that by using a powerful magnetic field and very low temperatures, below –450 degrees Fahrenheit (–270 degrees Celsius), they could read the state of electrons in a silicon wafer, potential qubits, using electrical current, and were able to extend the usable lifetime of those qubits dramatically.
Since reading out the state of the qubit, encoded in a property known as spin, is one of the main challenges to quantum computing, researchers will eventually need to be able to measure the spin state of a single qubit, much as classical computers can read and write to individual bits.
One way to do that is to map the quantum information onto a current flowing through a device. In other words, the researchers track a current flowing through the device as the spins are manipulated.
The problem is that the spin of the donor electrons doesn’t stay electrically readable for long, just two millionths of a second in previous studies using this kind of detection. The team extended the life of the spins 50 times by applying a strong magnetic field, some 25 times the strength of those used in previous experiments, to align the spins, along with lowering the temperature. Scaling down to single-spin sensitivity will be a challenge, especially given the propensity for electric currents to interfere with the spins.