The quantum computer has long been a dream for techies, physicists, and anyone who likes the idea of incomprehensible calculations performed at incomprehensible speeds. A research team at the Massachusetts Institute of Technology (MIT) has just taken a huge step toward that goal: They discovered that ultra-cold sodium-potassium molecules can likely function as the extremely stable “qubits” needed to make that fantasy a reality.
Just what are quantum computers, you ask? No one has ever made one, but people have been theorizing about them for almost a century. Such computers would encode information as qubits, or “quantum bits,” which would work with superpositions of 0’s and 1’s; in other words, bits of information would be encoded by both a 0 and 1, as opposed to either a 0 or a 1, like the computers we use now. Quantum computers would work so quickly that they would render our current computers totally meaningless — kind of like the typewriter in your grandma’s attic.
To create a quantum computer with these qubit building blocks, scientists need to achieve three major steps.
First of all, particles need to be trapped long enough to be co-opted for use.
Second of all, the particles need to be able to carry quantum information long enough to execute step three.
Third of all, the particles need to be able to interact with each other to perform the calculations.
Molecules are much better suited to the third step than atoms: “Typically, atoms have to really meet each other, be on top of each other almost, before they see that there’s another atom there to interact with,” Professor Martin Zwierlein told MIT News, “whereas molecules can see each other [from a relatively far distance away].”
The MIT team decided to use a sodium-potassium molecule for the experiments: It’s already a pretty stable molecule, and since it consists of only two atoms, it’s easier to cool and bring to an even more stable — and therefore controllable — state.
The team cooled these molecules down to only a few ten-millionths of a degree higher than absolute zero. At this temperature, the molecules were able to be trapped and carry quantum information for a period of one second.
That might not seem like a long time, but it is. Previous experiments have only been able to get particles to hold quantum information for a thousandth of a second, so this is a massive improvement. In fact, it’s the exact improvement that was needed to complete step two: The researchers estimate that such molecules will be able to do a calculation in a fraction of a millisecond, which means tens of thousands of calculations in one second, and that ratio “has been stated as one of the requirements for a quantum computer,” says Zwierlein.
So, steps one and two are looking pretty good. But don’t forget that other key aspect of creating a quantum computer: the third step, in which multiple qubit particles interact with each other. The MIT experiment was performed with just a single molecule; now that scientists know that the molecule is capable of holding quantum information for one second, they can attempt to get two of these molecules to perform a calculation together.
“If we can trap one molecule, we can trap two,” says Professor Sebastian Will. “And then we can think about implementing a ‘quantum gate operation’ — an elementary calculation — between two molecular qubits that sit next to each other.”
Once researchers can get hundreds of qubit molecules working together, they’ll be able to make a computer with capabilities that are far beyond anything a device can do now: something that could “carry out calculations so complex that no existing computer could even begin to check the possibilities,” explains MIT News.
Unfortunately, though, it may take a decade or more before such a computer can be made, the researchers told MIT News. But this is still an enormous and important step. It may be hard to imagine now, but something like the massively-talented Alienware “Threadripper” will seem like that typewriter compared to what’s coming.