One big challenge for quantum computing researchers is scale. They need to build a system that eventually can support thousands or even millions of quantum bits, or qubits—not just a few dozen—in order to make quantum computing practical and commercially viable.
Toward that objective, Intel and partner QuTech on Tuesday unveiled a technical paper at an international conference in San Francisco for a quantrum control chip called Horse Ridge designed to control up to 128 qubits. Some recent systems operate with about 50 qubits, but the ultimate goal is many thousands and possibly millions.
“We’re continuing to make steady progress toward making commercially viable quantum computing a reality in our future,” said Jim Clarke, director of quantum hardware at Intel Labs, in a statement.
Horse Ridge was first announced in December, but now Intel and QuTech are offering more details.
The chip itself is an integrated cryogenic System-on-Chip that measures just 4 x 4 mm2 and is implemented on Intel 22nm FFL (FinFET Low Power) CMOS technology. Functionally, it scrunches together digital core, analog/RF circuitry and SRAM memory to use microwave pulses to manage and manipulate the state of the qubits in a quantum system.
In addition to dealing with thousands of qubits at the same time, quantum researchers also need to maintain high levels of fidelity. The Horse Ridge chip is designed to reduce errors from phase shift in radio frequencies. Phase shift can result in undesirable cross talk.
To lessen phase shift, the researchers have integrated four radio frequency channels into a single Horse Ridge chip, with each controlling up to 32 qubits, by using frequency multiplexing. That’s a process of dividing bandwidth into frequency bands that don’t overlap with each other and each carry a separate signal. That means Horse Ridge potentially can control up to 128 qubits to help reduce the bulky cables and instruments used in the past.
Intel and QuTech explained that the four frequencies can be tuned precisely to allow the quantum system to automatically correct for phase shift, thereby improving fidelity. Horse Ridge is designed to work with a wide frequency range to control transmons (superconducting qubits) and spin qubits. Transmons typically operate between 6 GHz to 7 GHz, while spin qubits operate at 13 Ghz to 20 GHz.
In a technical spec sheet, Intel said its Horse Ridge chip can operate at 3 Kelvin, or minus 456.07 degrees Fahrenheit. That’s close to absolute zero, the temperature at which atoms stop moving.
QuTech is a partnership of TU Delft and TNO (Netherlands Organization for Applied Scientific Research). QuTech and Intel presented their research paper at the 2020 International Solid-State Circuits Conference.