Role of all-optical switches in quantum networking

Written by 

Rohit Kunjappa

Head of Product Management & Application Engineering

The role of and need for all-optical switching in the emerging quantum networking space is growing, and growing rapidly. The quantum networking space and, in particular, quantum communications holds the promise and potential to make previously impossible communications possible. 

Fortune Business Insights’ latest forecast estimates that between 2021 and 2028, the market will exhibit a CAGR of 30.8% growing to be worth $3.1 billion by 2028. To capitalise on this, the communications industry must ensure they have the right tools to begin and continue to adapt.

Quantum computing advantages  

Quantum computing utilises the fundamental principles of quantum mechanics to perform calculations. This will help address a number of problems that are prevalent in classical communication due to computational challenges such as processing power and storage. These include the following: 

  • Improving security by creating private keys for encryption for secure data transmission using QKD (Quantum Key Distribution)
  • Improving healthcare – in the design and analysis of molecules for drug development quantum computers can simulate the properties of the molecules that classical computers can not
  • Teleportation of information without physically transmitting the information from one location to another with a new quantum internet
  • Modelling and simulation of complex natural processes like weather and climate warming
  • Accelerating machine learning

 Creating a quantum network

Unlike classical computers, quantum computing uses quantum properties like superposition, entanglement, interference and uncertainty to achieve a deterministic outcome. Qubits are the basic unit of quantum information, carried or housed in a physical device like a chip or processor, and are the building blocks of quantum computing. 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, it multiplies the noise. 

In order to scale and commercialise quantum computing, quantum networking is required. Quantum networks will provide powerful and secure cloud quantum servers by connecting together and amplifying the capabilities of individual quantum processors. But how do we create this?

A key requirement for most quantum communication protocols is successful distribution. 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

Until a quantum internet is built, one of the many ways to realize qubits for larger, stable systems and to transmit over longer distances (potentially using quantum multiplexing with quantum error correction) is to send photon-based qubits over conventional DWDM communication networks to distribute entanglement and route quantum information to multiple nodes. 

There are, however, some challenges. With increase in distance travelled, the photon loss increases exponentially making it one of the biggest hindrances to quantum transmission. We also see that entanglement degrades or is destroyed with phase decoherence making quantum communication challenging and when you move beyond point-to-point communication, distributed synchronization is also an issue. 

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, in addition to amplifying the signal, also amplify noise, making them less than ideal for quantum transmission. All-optical switches that do not have to regenerate the signal the way OEO (optical-electrical-optical) 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 electrical format. The transparent nature of all-optical switches makes them protocol, format and data rate agnostic. 

With data rates increasing, all-optical switching is more relevant now than ever before. Some of the leading quantum research groups worldwide are performing cutting edge quantum networking research using POLATIS all-optical switches.