An ion trap with four segmented blade electrodes used to trap a liner chain of atomic ions for quantum information processing. Shantanu Debnath and Emily Edwards

Computer scientists have created a small programmable quantum computer that can run a number of quantum algorithms.

Quantum computers have the potential to be much faster than conventional computers but due to the physics underlying their creation they are difficult to program and reconfigure.


Now, a new, small, quantum computer has been built by a research team at the University of Maryland. It is one of the first significant steps towards scaling up the devices.

"We tried to make a quantum processor of five qubits with trapped ions that is reconfigurable, and by that I mean that you can literally program algorithms into it," Shantanu Debnath, the lead author of the Nature paper, from the US university told WIRED.

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He calls it a "fundamental building block" towards large scale devices.

Using laser pulses, which can be turned on and off, the academics were able to implement the quantum algorithms. "It's really the flexibility that we are aiming towards and we have done," he said.


Debnath explains: "We demonstrated this by implementing four different algorithms and we are running more right now. In trapped ions, or any other computing platform, this had not been done before".

The device is made up of five pieces of quantum information – known as qubits. Traditionally bits can only ever be in the state of 0 or 1, but a qubit can be a supposition of both.

An ion trap with four segmented blade electrodes used to trap a linear chain of atomic ions for quantum information processing. Shantanu Debnath and Emily Edwards

In reality this means a large-scale quantum computer (which has not yet been achieved) would be made of many qubits that can answer multiple questions at once. Such a device would be much faster than any computer that exists today and would be able to process multiple things at once.

In the research the academics – which involved those from the Joint Quantum Institute – were able to use algorithms to perform a mathematical calculation in a single step. A conventional computer would require several steps to complete the same tasks.


"The team implements three quantum algorithms using their systems, demonstrating the power of their control techniques," Andrew Daley, from the University of Strathclyde physics department, told WIRED. "It’s really nice to see this being done with trapped ions, and provides an exciting platform for future developments," said the independent researcher.



Daley, chair of theoretical quantum optics and research director at the Scottish university, says the work is representative of a "general shift" in the approach to prototyping quantum computers. "This provides a system that in a sense is ready to be scaled up to a fully error-corrected quantum computer (although this challenge is naturally far from trivial)," he says.

Now the Maryland researchers plan to start working on exactly this. "The next step is to miniaturise the system; to come up with a compact version," Debnath explains. "This means improving the ion trap, improving the way you deliver the lasers and all your controls into the system. Also, to scale it up and have more qubits in the processor."

The theory behind this has yet to be completely proved but the latest work does allow for the scaling to be started.