Quantum computing: How basic broadband fiber could pave the way to the next breakthrough


Google’s Sycamore quantum processor. 

Picture: Google

The usefulness of most quantum computer systems remains to be considerably restricted by the low variety of qubits that hardware can assist. However easy fiber optic cables – similar to those used for broadband connections – may very well be the reply. 

A workforce of researchers from the Nationwide Institute of Requirements and Expertise (NIST) discovered that, with just some tweaks, optical fiber can be used to communicate with the qubits sitting inside superconducting quantum computer systems, with the identical degree of accuracy as present strategies.

In contrast to the steel wires presently used, it’s straightforward to multiply the variety of fiber optic cables in a single system, which suggests it’s doable to speak with extra qubits. In response to NIST, the findings pave the best way to packing 1,000,000 qubits right into a quantum laptop. Most gadgets presently assist lower than 100.  

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Superconducting quantum computer systems, reminiscent of those that IBM and Google are constructing, require qubits to sit down on a quantum processor that’s cooled to a temperature of 15 milikelvin – colder than outer house – to guard the particles’ extraordinarily fragile quantum state.  

However whether or not to regulate the qubits or measure them, researchers first want to speak with the processor. This implies a connection line should be established between room-temperature electronics and the cryogenic surroundings of the quantum circuit. 

Usually, scientists use microwave pulses to speak with qubits. With completely different frequencies and durations, the pulses can affect the state of the qubit; or researchers can take a look at the amplitude of the mirrored microwave sign to “learn” qubit-based info. 

Microwave pulses are usually despatched all the way down to the ultra-cold qubits by coaxial steel cables. This comes with a sensible drawback: units of steel cables can be utilized to attach with to as much as 1,000 qubits, after which it turns into bodily unworkable to construct extra wiring in a single system. 

But firms have bold objectives in terms of scaling up quantum computer systems. IBM, for instance, is predicted to surpass the 1,000 qubit mark by 2023 with a processor referred to as IBM Quantum Condor, and is eyeing a long-term aim of a million-qubit quantum system. 

John Teufel, a researcher at NIST who labored on the institute’s newest analysis, explains that coaxial steel cables will not reduce it for for much longer. “The main focus of most real-life quantum computing efforts has been to push ahead utilizing typical wiring strategies,” Teufel tells ZDNet. 

“Whereas this has not but been the bottleneck for state-of-the-art programs, it would develop into necessary within the very close to future…All the businesses which are pursuing quantum-computing efforts are nicely conscious that new breakthroughs will probably be required to achieve their final aim.”


The researchers opted to exchange steel cables with acquainted optical fiber know-how.  

Picture: NIST

To deal with this challenge, Teufel and his workforce at NIST opted to exchange steel cables with acquainted optical fiber know-how, which, based mostly on a glass or plastic core, was anticipated to hold a excessive quantity of alerts to the qubits with out conducting warmth. 

Utilizing typical know-how, the researchers transformed microwave pulses into mild alerts that may be transported by the optical cables. As soon as the sunshine particles attain the quantum processor, they’re transformed again into microwaves by cryogenic photodetectors, after which delivered to the qubit.  

Optical fiber was used to each management and measure qubits, with promising outcomes: the brand new set-up resulted in correct rendering of the qubit’s state 98% of the time, which is identical accuracy as obtained utilizing common coaxial traces. 

Teufel and his workforce now envision a quantum processor during which mild in optical fibers transmits a sign to and from the qubit, with every qubit speaking to a wire. “In contrast to typical steel coaxial cables, the fiber itself isn’t the bottleneck for what number of qubits you might speak to,” says Teufel. “You may merely give every qubit a devoted fiber by which to ship alerts, even for a million-qubit system. 1,000,000 fibers appears possible, whereas 1,000,000 coaxial traces doesn’t.” 

One other benefit of optical cable, notes Teufel, is the data carrying capability of a single fiber, which is far higher than that of a steel cable. Many extra alerts – as much as a number of thousand – may be despatched by one optical wire, and the scientist envisions separating and re-routing these alerts to completely different qubits within the processor. This is able to successfully allow a single fiber optic cable to speak to a number of qubits without delay. 

The experiment is but to be carried out. Within the meantime, Teufel is assured that every one eyes will probably be on NIST’s newest findings. “Novel wiring strategies, just like the one we have now proven right here, will ultimately be required to take care of the unimaginable progress trajectory of quantum computing efforts,” says Teufel. 

“We don’t counsel that our new methodology is the one long-term answer, however we’re excited to see that this new thought seems extremely promising. I anticipate that firms will probably be trying carefully at this work to see if these new strategies may be integrated into their future methods.”