“For many years, people said that it was completely impossible to construct an actual large-scale quantum computer,” says Winfried Hensinger, head of the Ion Quantum Technology Group at Sussex. “With our work, we have not only shown that this can be done but have put forward a nuts and bolts construction plan to build a real large-scale machine.”

A comprehensive quantum computer that can solve complicated problems (such as factoring large numbers or simulating complex chemical reactions) exponentially faster and more efficiently than is possible with current classical computing could revolutionize our lives.

Microwave fields and integrated current-carrying wires

Trapped ions can be used as quantum bits (qubits) in such machines. Unlike previous trapped-ion quantum-computer architectures, the new set up executes quantum gates thanks to voltages applied to a quantum microchip in conjunction with global microwave fields and integrated current-carrying wires, explains Hensinger. “We read out the quantum states of each ion via detectors integrated in the chip and all the electronics are attached to the backside of the chip, generating and controlling voltages on the chip. Ions can be transported from one module to another using electric fields, thereby transmitting quantum information between modules.”

The chip modules control all operations as stand-alone units, are constructed using microfabrication techniques, and are within reach of current silicon-based fabrication technologies, he adds.

Fully modular large-scale machine

The fact that actual quantum bits can be transmitted between individual quantum computing modules allows us to make a fully modular large-scale machine capable of reaching nearly arbitrary large computational processing powers, he tells nanotechweb.org. “Once built, such a computer would have the potential to answer many questions in science: create new, lifesaving medicines; solve the most mind-boggling scientific problems; in general crack problems that an ordinary computer would take billions of years to do.”

 The researchers have estimated, for example, that calculating a well-known problem in the quantum field (prime factoring of a 2048-bit number) would take just 110 days and require a system of 2 × 108 trapped ions. Further tweaks to the computer’s error correction code could drastically reduce these figures too.

Constructing a prototype

Many problems still need to be overcome though. For instance, creating the strong magnetic field gradients and well controlled voltages needed to make the quantum computer work will be no easy task but the Sussex team is busy constructing a prototype based on its technology as we speak.

“It is difficult at this stage to estimate the full impact that quantum computers may have on our world but it may be similar to how classical computers changed all our lives forever,” says Hensinger.

The blueprint is described in Science Advances DOI: 10.1126/sciadv.1601540.

For more on the latest developments using nanostructures in quantum information processing visit the Nanotechnology focus collection.