How would you find a rabbit hidden in one of a million hats? If you used a present-day computer program, it would check each of the million hats, one at a time.
A quantum computer, however, “peeks into all 1 million hats at the same time and sees the rabbit in one step,” said Sergey Frolov, assistant professor in the University of Pittsburgh’s Department of Physics and Astronomy.
Quantum computers use principles of quantum mechanics — a field that, put simply, studies nature at the atomic level. Computers built with quantum physics principles in mind have the potential to solve some of the universe’s most complex problems — fast. And not just fast, Frolov said. Exponentially faster, meaning that without them, the problem would not be solved before the sun dies. But performing these speedy calculations will require new hardware.
Faster, Stronger, Smarter
Pitt is racing to create quantum computers that could help solve computational challenges totally inaccessible to present-day computers. Here are a few facts to know:
- Quantum processors can be potentially millions of millions of times faster than current computers.
- The speed is caused by superposition — a quantum system in which something can be up and down at the same time — and entanglement, wherein similar particles are linked even millions of miles apart.
- Quantum bits, or “qubits” for short, are the building blocks of a quantum computer. While bits in modern-day devices can be either in state 0 or state 1, qubits can be in both states simultaneously.
In the race to create quantum computers, Pitt is leading an international team of universities, research centers and corporations to discover the best materials for building these speedy machines. The work will be supported by a $4.8 million grant from the National Science Foundation (NSF) under its Partnership for International Research and Education (PIRE) program. Along with Frolov, Department of Physics and Astronomy researchers Hrvoje Petek, Michael Hatridge and David Pekker will serve as the project’s co-principal investigators.
Pitt will lead the five-year collaboration with Carnegie Mellon University; the University of California, Santa Barbara; French partners from the Centre National de la Recherche Scientifique and Commissariat à l'énergie atomique et aux énergies alternatives; and industrial partner Microsoft Research. The groups will explore combining hybrid materials — disparate materials like aluminum semiconductors and silicon superconductors — into a single structure for quantum science and technology. The PIRE program will bring together materials engineers, surface scientists, computational chemists and physicists, as well as students from all levels at Pitt. Researchers will also have the opportunity to conduct research in France.
“Compared with robotics or medical research, quantum research may seem like a niche, but it can have a paradigm-shifting effect for our information technology industry and, at the same time, for the way we think about our universe,” Frolov said.
The NSF, the European Union and industry giants Google, IBM, Intel and Microsoft have prioritized research into quantum computing, which Frolov said “would unlock revolutionary computing powers based on the principles of quantum superposition and entanglement." (See sidebar.)
Researching an unusual particle
The new project also gives the team the chance to build upon discoveries of an unusual particle Frolov and colleagues made in 2012 at Delft University of Technology in the Netherlands. Frolov, a postdoctoral fellow at the time, was part of a team that created an exotic and never-before-seen particle known as the Majorana fermion, which he theorizes could help quantum computers process faster. These particles are also antiparticles at the same time, so they combine matter and antimatter in the same object, he said.
Majorana fermions were first theorized in the 1930s by physicist Ettore Majorana, who proved that a particle could live on the border between matter and antimatter, both of which are a result of an energy burst like the Big Bang, with the exotic latter being a mirror image of the former. Frolov and his colleagues were the first to produce these particles in a lab, and their paper on the achievement made the cover of the prestigious journal Science in 2012 and earned them the American Association for the Advancement of Science’s 2012 Newcomb Cleveland Prize, an annual honor awarded to the author or authors of the best research article or report appearing in the journal.
“We have been trying to put our findings on firmer ground since, and we have realized that to do that we need to invent new materials — namely hybrid materials,” Frolov said. “Hybrid materials should allow us to harness Majorana fermions for use in quantum computers.”
Quantum information is inherently fragile, so the materials requirements for quantum computers are more stringent than for classical computers. Those hybrid materials might take the form of “sandwiches” of superconductors and semiconductors.
Superconductors can transfer electrical signals without any loss or heating. Semiconductors are used to fabricate microchips in laptops, desktop computers, smartphones and tablets. Together, the two materials could lead to computer chips fast enough and strong enough to handle quantum computing, Frolov said.
The project team also will study the effect of crystal growth. All computer chips are crystals, and the quality of those crystals sets limits on performance, Frolov said. Just as plants grow from seeds in soil, crystals grow from seeds called catalysts. In this case, catalysts are gold particles one millionth the thickness of a human hair. The researchers will expose these catalysts to heat and chemicals in order to grow the crystals for quantum computers.
“Pitt is going to lead an effort in the discovery of the next generation of materials tailored for quantum processors,” Frolov said.