NEW HAVEN — A team of Yale University physicists has achieved a major advance toward creating an elusive superfast quantum computer that would assist research in fields such as high-level encryption.
The scientists have created the first rudimentary solid-state quantum processor, according to an article published Sunday on the journal Nature’s Web site.
“In many ways it looks like our idea of a computing processor,” said Leonardo DiCarlo, a postdoctoral associate in applied physics at Yale’s School of Engineering and Applied Science and lead author of the paper. “It’s a chip. It has wires that come in and come out without any lasers or magnets.”
What the processor does has been achieved before; the scientists’ excitement is that they’ve created a simple processor that could be made using “conventional fabrication technology,” according to DiCarlo, that could be “scaled up” to become more powerful and conceivably could be manufactured.
“Our processor can perform only a few very simple quantum tasks, which have been demonstrated before with single nuclei, atoms and photons,” said Robert Schoelkopf, professor of applied physics and physics at Yale. “But this is the first time they’ve been possible in an all-electronic device that looks and feels much more like a regular microprocessor.”
One practical use for a quantum computer would be high-level encryption, DiCarlo said.
“Encryption can be made totally secure because anyone who was trying to break the code would be found out,” he said. “He will corrupt the data in ways that you can check.”
Quantum computing would enable both encryption and the ability to break others’ codes, DiCarlo said.
Quantum processing depends on quantum bits or qubits. Whereas a bit represents 0 or 1, a qubit can switch between 0, 1 or be placed in a “superposition” of simultaneous multiple states, enabling massive parallel computing, DiCarlo said.
While difficult to understand without a degree in quantum physics, the end result is an immense increase in information storage and processing power, according to the Yale team.
For example, in order to determine which of four phone numbers is the one for Radio Shack, you’d have to dial them one at a time. A quantum processor, however, using parallel computation, simultaneously determines the correct number and dials it.
“We’re still far away from building a practical quantum computer, but this is a major step forward,” Schoelkopf said.
A qubit is made up of a billion aluminum atoms, but acts like a single atom, the Yale team said. What the scientists created was a two-qubit superconducting chip, which they used to run computations such as a simple search.
The problem for quantum physics researchers is that qubits are ephemeral. The first qubits maintained quantum states for a nanosecond, one-billionth of a second, but the Yale team managed to keep them for a microsecond, 1,000 times longer, giving them time to make the necessary computations.
In order for two qubits to communicate with one another, the Yale team developed a “quantum bus,” in which photons transmit information through wires connecting the qubits. The trick was to get the qubits to switch “on” and “off” abruptly, when the researchers wanted them to, DiCarlo said.
The next steps are to lengthen the qubits’ quantum states and to connect more together. The processing power increases exponentially with each additional qubit, Schoelkopf said.
The team was led by Steven Girvin, professor of physics and applied physics. Other authors of the paper from Yale were Jerry M. Chow, Lev S. Bishop, Blake Johnson, David Schuster, Luigi Frunzio and Steven Girvin.