Prototype chip could carve the path for practical quantum computers

Original news release was issued by the Massachusetts Institute of Technologywritten by Larry Hardesty.
Once thought to be unattainable, quantum computers are slowly growing to overthrow the current computing leaders. With superior processing power and overall computing speed, these hypothetical devices could offer hope for solving problems in wide variety of fields which require more robust computing, such as cryptography, software engineering, information systems and many more. Quantum computers could potentially pocket their conventional baby brothers by performing some calculations much more rapidly with quantum bits, or qubits, which can represent 0 and 1 simultaneously.
Even though the development of quantum computing is still in its infancy, researchers from MIT and MIT Lincoln Laboratory report an important step forward toward practical quantum computers, presenting a prototype chip that can trap ions in an electric field and, with built-in optics, direct laser light toward each of them. The key difference that propels this research beyond what was already researched and tested lied in devising a new method of trapping ions, which is considered to be the most widely studied qubit technology. The previously used — standard ion trap — looks like a tiny cage, whose bars are electrodes that produce an electric field with ions lined up in the center. The new surface trap consists of a chip with electrodes embedded in its surface and ions hovering 50 micrometers above them. While the cage trap is limited in size, the surface trap could, in principle, be extended indefinitely, allowing for many more qubits to be stored inside.

If you were wondering where the major obstacle to be overcome is, here comes the tricky part. Performing a quantum computation requires precisely controlling the energy state of every qubit independently, via laser beams. In a surface trap, the ions are only about 5 micrometers apart so hitting each ion with an external laser without disturbing the neighboring ones is incredibly difficult. However, two research groups managed to successfully tackle the problem. The group led by Rajeev Ram, an MIT professor of electrical engineering and one of the senior authors on the paper, designed and built a suite of on-chip optical components that can channel laser light toward individual ions. The other group, under the supervision of Jeremy Sage, who together with John Chiaverini leads Lincoln Laboratory’s trapped-ion quantum-information-processing project, accommodated the surface trap with integrated optics without compromising its performance.

“Typically, for surface electrode traps, the laser beam is coming from an optical table and entering this system, so there’s always this concern about the beam vibrating or moving,” Ram says. “With photonic integration, you’re not concerned about beam-pointing stability, because it’s all on the same chip that the electrodes are on. So now everything is registered against each other, and it’s stable.”

Although the prototype proved to be a success, there is still a long way to go before the first conventional quantum computer sees the light of day. The addition of light modulators is in the works, which would allow qubits to simultaneously receive light of different, time-varying intensities, thus making the programming more efficient. “Arguably, the most important area in which progress needs to be made is technologies which will enable the systems to be scaled up to larger numbers of qubits, as was so impressively addressed by this research” said David Lucas, a professor of physics at Oxford University. It would appear, the era of practical quantum computers might be nearing us qubit by qubit.

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