Intel has announced wave two of its Horse Ridge cryogenic control chip, with the company touting it as another milestone in its progress toward overcoming scalability, one of quantum computing's biggest hurdles.
Horse Ridge II builds on the company's first-generation controller.
"Like with any product that we make, there are usually several iterations, some based on things we've learned in the first iteration of the actual chip, and in this case, not only improvements that we want to make to the actual chip, but also we're learning some things about the way our qubits should be controlled," director of quantum hardware at Intel's components research group Jim Clarke said.
Speaking with ZDNet about the announcement, Clarke said when Intel developed Horse Ridge I, it focused on being able to control a few different qubit -- quantum bit -- types, mainly a superconducting qubits and silicon qubits. Intel over the last couple of years has gravitated away from the superconducting qubit that other companies like IBM and Google are studying to more of a qubit that looks like a transistor.
"We're focused on silicon qubits and our second version of Horse Ridge is more geared towards our silicon spin qubits," he said.
Horse Ridge II, Intel says, supports "enhanced capabilities and higher levels of integration for elegant control of the quantum system". New features include the ability to manipulate and read qubit states and control the potential of several gates required to entangle multiple qubits.
Horse Ridge II builds on the first-generation system-on-chip (SoC) ability to generate radio frequency pulses to manipulate the state of the qubit, known as qubit drive.
"With Horse Ridge I, we essentially were able to drive the qubit, basically apply signals that would manipulate the state of the qubit between 0-1; with Horse Ridge II, we can not only drive the qubit, but we can read out the state of the qubit, we can apply pulses that would allow us to control the interaction between two qubits, and so we've added additional controller capabilities to Horse Ridge II," Clarke said.
"We have a very programmable filter that would allow us to send a variety of different pulse shapes to control our qubits, we have an integrated microcontroller, we have a lot of DACs -- digital to analogue controllers -- that would allow us to control the individual qubits to a greater extent and these DACs would otherwise be discrete boxes in a control rack external to the refrigerator, so we're starting to take some of these boxes and put them into our SoC inside of our qubit refrigerator."
Horse Ridge II is implemented using Intel 22nm low-power FinFET technology and its functionality has been verified at four kelvins -- 4 degrees above absolute zero.
Intel said the addition of a programmable microcontroller operating within the integrated circuit enables Horse Ridge II to deliver higher levels of flexibility and sophisticated controls in how the three control functions are executed. The microcontroller uses digital signal processing techniques to perform additional filtering on pulses, helping to reduce crosstalk between qubits.
"This chip has north of 100 million transistors on it, so it's an advancement over Horse Ridge I," Clarke added.
"At Intel, our goal is to develop a system, a quantum computer, and that quantum computer is comprised of many things. It's comprised of the quantum processor, our qubit control, the architecture and the algorithm."
One of the reasons that Intel expects to win in the quantum space is that it's relying on its expertise in classical computing.
"What sets Intel apart in this space … for one, we're choosing a qubit that looks like a transistor, so the premise of all of this is that Intel is really good at making transistors," he explained. "The second is we're relying on our transistor technology to build very customised control methods to control those qubits. If our qubits look like transistors, we're also relying on our transistor technology to control those."
According to Clarke, quantum computing is being approached by many as something very different to classical computing.
"Indeed quantum computing will be able to do things that no supercomputer on Earth can do, so it represents an inflection point or an opportunity for the future of computing, with that, it would be easy for people to forget that this future of computing still relies on classical computing to accomplish our goal," he said.
"We're relying on our expertise to a classical computing to help us fabricate these quantum chips and second, we're relying on classical computing to control our quantum chips."
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