Ready, Set, Switch: The Role of All-Optical
Switches in Quantum Networks

These cutting-edge switches help to address one of the key barriers to a quantum internet by ensuring information that could be lost or distorted travels safely at high speeds, switching all light regardless of wavelength.

processors. But how do we create this? Unlike classical computers and contrary to popular perception, quantum computing isn’t just a faster Internet; it is something entirely different. Quantum computing uses quantum properties like superposition, entanglement, interference, and uncertainty to achieve a deterministic outcome—the basis for quantum physics.

Qubits are the basic unit of quantum information, carried or housed in a physical device like a chip or processor. You increase the computational potential by increasing the number of qubits that can be processed into controllable quantum states. It is difficult to add more qubits as they are very sensitive to environmental factors like noise, meaning they have very low fault tolerance. When you add qubits, the noise is multiplied.

So, unlike classical computers, which only have their computational power determined by their CPU, a quantum computer’s computational power will be able to grow depending on the number of qubits it processes. A key requirement for most quantum communication protocols will be successful distribution. Therefore, to enable many-to-many—networked—quantum communications, a new type of switch capable of routing entangled single photons is needed.

The role of all-optical switches

The role of and need for all-optical switching is growing—and growing rapidly. But until a quantum Internet is built, one of the many ways to realize qubits for larger, stable systems and to transmit over longer distances is to send photon-based qubits over conventional networks, distributing entanglement and routing quantum information to multiple nodes.

There are, however, some challenges. With increases in distance traveled, the photon loss grows exponentially, making it one of the biggest hindrances to quantum transmission. We also see that entanglement degrades or is destroyed with phase decoherence, while moving beyond point-to-point communication can lead to issues with distributed synchronization, making quantum communication challenging.

All-optical switches (OOO) function by selectively switching the entire optical signal on one optical fiber to another optical fiber. Traditional optical-electrical-optical (OEO) switches have a challenge preserving quantum coherence and optical amplifiers will amplify noise as well as the signal, making them less than ideal for quantum transmission. All-optical switches that do not have to regenerate the signal the way OEO switches do have a higher probability of going longer distances and preserving quantum coherence. Therefore, all-optical switches have a unique value proposition over traditional OEO switches as they transmit the original input light signal through a transparent all-optical switch core, without converting it into an electrical format. The transparent nature of all-optical switches makes them protocol-, format- and data-rate agnostic.

Some of the leading quantum research groups worldwide are performing cutting-edge research using all-optical switches. These cutting-edge switches help to address one of the key barriers to a quantum internet by ensuring information that could be lost or distorted travels safely at high speeds, switching all light regardless of wavelength. However, although this technology promises to transform how we connect with the world, we still don’t know the full capabilities of the quantum network, nor when it will be widely operational.    

For a truly successful network to become a reality, the industry needs to bring together all the necessary pieces of technology. This can only be done if robust quantum communication ‘ecosystems’ are developed through partnerships and alliances between telecom providers, start-ups, established businesses and research institutions. It will be critical that everyone works together to set standards, develop solutions, and cultivate workers with the right skills for the operation of the network.

There is one thing we know for sure, however: networks 10 years from now are going to be unrecognizable, and that prospect is extremely exciting.


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