An IBM-led team of researchers has developed the world’s most advanced quantum computer, solving problems that are difficult for conventional computers at a much faster speed.
Quantum computers get their power by taking advantage of certain quantum physics properties of atoms, or nuclei, that allow them to work together as quantum bits, or ‘qubits’, to be the computer’s processor and memory. By interacting with each other while being isolated from the external environment, theorists have predicted – and this new result confirms – that qubits could perform certain calculations exponentially faster than conventional computers.
“Quantum computing begins where Moore’s Law ends – about the year 2020, when circuit features are predicted to be the size of atoms and molecules,” says Isaac Chuang, who led the team of scientists from IBM Research in San Jose, California, Stanford University and the University of Calgary. “Indeed, the basic elements of quantum computers are atoms and molecules.”
The new quantum computer contains five qubits – five fluorine atoms within a molecule designed so the fluorine nuclei’s spins can interact with each other as qubits, be programmed by radiofrequency pulses and be detected by nuclear magnetic resonance instruments similar to those used in hospitals and chemistry labs.
Using the molecule, Chuang’s team solved in one step a mathematical problem for which conventional computers require repeated cycles. The problem is called ‘order-finding’ – finding the period of a particular function – which is typical of many basic mathematical problems that underlie important applications, such as cryptography.
To understand the order-finding problem, consider a large number of rooms and an equal number of randomly placed one-way passages, some of which may loop back upon themselves into the same room. It is certain that at some point, a person moving through the rooms and passages will return to the starting room.
The problem is to calculate with the least number of queries, the minimum number of passages through which one must travel before returning to the starting room. IBM Research’s 5-qubit quantum computer solved any case of the problem in one step, while a conventional approach would require up to four steps. The result confirmed predictions of Professor Richard Cleve of the University of Calgary in Canada earlier this year.
But the challenges remain daunting. IBM’s 5-qubit quantum computer is a research instrument. Commercial quantum computers are still many years away, since they must have at least several dozen qubits before difficult real-world problems can be solved.