The Quest for Scalable Quantum Computers Presses On

Following a year of rapid growth, quantum computing stocks experienced an abrupt slowdown just days into the International Year of Quantum Science and Technology. This shift was sparked by Nvidia CEO Jensen Huang’s CES 2025 keynote, where he projected that “very useful quantum computers” are likely still twenty years away.

Figure 1. Fiber-Optic Technology Powers a Major Leap in Quantum Computing.

Despite market volatility and lingering industry doubts, the pursuit of scalable quantum computers remains fierce. These advanced machines promise to surpass classical computers in specific computational tasks, but overcoming substantial technical hurdles is essential before they can achieve practical, widespread use. Figure 1 shows Fiber-Optic Technology Powers a Major Leap in Quantum Computing.

Breakthrough in Quantum Hardware Scaling

A team of physicists from Professor Johannes Fink’s group at the Institute of Science and Technology Austria (ISTA) has made a significant advancement in quantum computing. They’ve developed a method that enables qubits to communicate through fiber optics, drastically reducing the reliance on bulky cryogenic hardware. “This new approach might allow us to increase the number of qubits so they become useful for computation,” explains Georg Arnold, co-first author and former PhD student in the Fink group. “It also lays the foundation for building a network of superconducting quantum computers connected via optical fibers at room temperature.”

The Challenges of Integrating Fiber Optics with Quantum Systems

Although fiber optics have transformed the telecommunications industry with faster, more efficient data transmission, applying them to quantum hardware is highly complex. Superconducting quantum computers, which rely on the unique properties of materials cooled near absolute zero, pose their own set of challenges.

To create superconducting qubits, tiny electrical circuits are cooled to temperatures just a few thousandths of a degree above absolute zero—colder than outer space—allowing them to lose all electrical resistance and maintain a continuous current. “Superconducting qubits are electrical by definition. To make them, we must reach temperatures of only a few thousandths of a degree above absolute zero,” Arnold explains.

Superconducting Qubits and Their Cold Reality

Despite their revolutionary potential, superconducting qubits face fundamental challenges. Electrical signals, commonly used to read and control qubits, suffer from low bandwidth, are easily disrupted by noise, and prone to information loss. Moreover, the wiring needed for these signals generates significant heat, complicating the already demanding cryogenic cooling required to maintain superconductivity. The process of “qubit readout”—detecting and measuring qubits via reflected electrical signals—demands colossal cooling infrastructure alongside complex, costly electrical components for filtering and amplification.

In contrast, higher-energy optical signals, such as those at telecom wavelengths, travel through thin optical fibers with minimal losses, lower heat dissipation, and much higher bandwidth. Using these optical signals to enhance superconducting quantum hardware would be ideal—if only qubits could "understand" them.

‘Translating’ Optical Signals for Qubits

Achieving a fully optical readout for superconducting qubits required the ISTA team to develop a way to "translate" optical signals into a language qubit could comprehend.

“Ideally, one would try to eliminate all electrical signals since the wiring introduces heat into the cooling chambers where the qubits are housed. But this isn’t feasible,” explains Thomas Werner, co-first author and PhD student in the Fink group at ISTA.

To bridge this gap, the researchers employed an electro-optic transducer to convert optical signals into microwave frequencies—an electrical form compatible with qubits. The qubits, in turn, reflect microwave signals, which the transducer converts back into optical signals.

“We demonstrated that we can send infrared light close to the qubits without compromising their superconductivity,” says Werner. By using the electro-optic transducer as a switch, the team successfully linked qubits directly to the outside world through optical connections.

Breaking the Qubit Barrier: A Scalable Future

Performing practical quantum computations will require thousands, if not millions, of qubits. However, the current infrastructure struggles to keep pace, with cryogenic cooling requirements posing a major bottleneck. “Our technology significantly reduces the heat load associated with measuring superconducting qubits. This advancement will help us break the qubit barrier and scale quantum computing to new heights,” says Georg Arnold.

The shift to fully optical readouts also allowed the researchers to eliminate many cumbersome electrical components. Traditional systems rely heavily on error-prone electrical signals, necessitating extensive signal correction hardware, all of which require cryogenic cooling. “By disconnecting the qubits from traditional electrical infrastructure using the electro-optic transducer, we replaced most of the setup with optical components,” Werner explains. This transformation not only enhances system efficiency and robustness but also reduces operational costs.

Connecting Quantum Computers with Light

Beyond individual qubit performance, this technology opens the door to linking multiple quantum computers using optical fibers. Currently, quantum systems rely on large dilution refrigerators to cool both processors and their connecting hardware.

“But these refrigerators have size and capacity limits,” notes Arnold. As space and cooling demands restrict qubit scalability, optical connections offer a promising solution. The team believes that connecting qubits housed in separate dilution refrigerators via optical fibers is now within reach. “The infrastructure is already in place, and we now have the technology needed to build the first simple quantum computing networks,” Arnold adds.

A Step Toward Quantum Networks

While this breakthrough marks a critical milestone in superconducting quantum hardware development, there’s still considerable work ahead. “Our prototype’s performance is currently limited, especially concerning the optical power required and dissipated,” acknowledges Arnold. “Nevertheless, it’s a proof of principle that fully optical readout of superconducting qubits is possible. Moving forward, it will be up to the industry to refine and scale this technology.”

Source: SciTECHDaily

Cite this article:

Priyadharshini S (2025), Quantum Computers Receive a Major Boost with Fiber-Optic Technology, AnaTechmaz, pp. 200