Thanks to a new technology dubbed dual band stabilization, Toshiba’s research team has broken a new record for optical fiber-based quantum communications.
Toshiba researchers have successfully sent quantum information over 600 kilometers of optical fiber, setting a new distance record and paving the path for large-scale quantum networks that might be used to securely share data across cities and even countries.
Thanks to a new technology that stabilizes the environmental fluctuations occurring in the fiber, the scientists demonstrated that they could transmit quantum bits (or qubits) over hundreds of kilometers of optical fiber without scrambling the fragile quantum data encoded in the particles, working from the company’s R&D lab in Cambridge, UK.
This might go a long way toward enabling the development of a next-generation quantum internet capable of spanning global distances, as experts expect.
The quantum internet, which will be a worldwide network of quantum devices linked by long-distance quantum communication links, is projected to enable use-cases that are currently unattainable with web applications. They range from building nearly unhackable communications to clusters of interconnected quantum devices that could collectively outperform the computation capability of old devices.
Quantum devices, on the other hand, must send and receive qubits – small particles that exist in a unique, but highly fragile, quantum state – in order to communicate. For years, scientists around the world have been trying to figure out the best way to transport qubits without causing them to lose their quantum state.
Qubits are shot down optical fibers that connect quantum devices in one approach. Small changes in the environment, such as temperature swings, cause the fibers to expand and contract, potentially interfering with the qubits.
This is why optical fiber tests have often been confined to a range of hundreds of kilometers; in other words, not nearly enough to establish the large-scale, global quantum internet that scientists have imagined.
Toshiba researchers devised a novel approach termed “dual band stabilization” to deal with unstable situations inside optical fibers. Two signals with different wavelengths are sent down the optical fiber in this manner. Two signals with different wavelengths are sent down the optical fiber in this manner. The first wavelength cancels out quickly fluctuating disturbances, while the second wavelength, which is the same wavelength as the qubits, is utilized to make finer phase adjustments.
Simply put, the two wavelengths combine in real time to counteract environmental disturbances inside the fiber, allowing qubits to transit securely over 600 kilometers, according to Toshiba’s researchers.
The company’s team has already utilized the technology to test one of quantum networks’ most well-known applications: quantum-based encryption.
Quantum Key Distribution (QKD) is a protocol that uses quantum networks to establish security keys that are hard to hack, allowing users to securely communicate sensitive information such as bank statements or medical records across an untrustworthy communication channel like the internet.
During a communication, QKD encrypts a piece of data by encoding the cryptographic key onto qubits and transferring those qubits to the other party through a quantum network. However, according to quantum mechanics constraints, it is impossible for a spy to intercept qubits without leaving a sign of eavesdropping visible to the users, who can then take precautions to protect the information.
Unlike traditional cryptography, QKD relies on the laws of physics to solve security keys rather than the mathematical complexity of solving them. Even the most powerful computers would be unable to crack the keys based on qubits. It’s simple to see why the concept is attracting interest from a wide range of stakeholders, including financial institutions and intelligence agencies.
The researchers were able to perform QKD over a significantly longer distance thanks to Toshiba’s novel technology for reducing optical fiber irregularities. “This is a very exciting result,” said Mirko Pittaluga, a Toshiba Europe research scientist. “With the new techniques we have developed, further extensions of the communication distance for QKD are still possible and our solutions can also be applied to other quantum communications protocols and applications.”
Toshiba’s 600-kilometer milestone for QKD utilizing optical fiber is a world record, according to the company, and will allow secure linkages to be established between cities such as London, Paris, Brussels, Amsterdam, and Dublin.
Other research groups, on the other hand, have concentrated on various methods for transmitting qubits, allowing QKD to occur over even greater distances. Chinese scientists, for example, have just completed QKD over a total distance of 4,600 kilometers utilizing a combination of satellite-based transmissions and optical fibers on the ground.
Every option has advantages and disadvantages: satellite technologies are more expensive and may be more difficult to scale up. But one thing is certain: research groups in the United Kingdom, China, and the United States are working hard to make quantum networks a reality.
Toshiba’s study was supported in part by the European Union, which is intent on creating quantum communications. Meanwhile, quantum networks have a specific position in China’s newest five-year plan, and the US just produced a blueprint laying out a step-by-step path to the creation of a global quantum internet.