Henry Semenenko

Measurement-device-independent quantum key distribution (MDI-QKD) offers a method of distributing shared randomness for use in symmetric key cryptography, while integrated optics provides a promising platform for ubiquitous quantum communication. This work experimentally demonstrates the use of indium phosphide (InP) devices for MDI-QKD. We generate 100 ps pulses for 2 GHz clocked, time-bin encoded BB84 states with random phases through a novel gain switching technique. By interfering two independent InP devices, we achieve 50 bps at 100 km and pre-empt the availability of integrated receivers which will increase rates through inherent scalability.

Recently, the first integrated Measurement Device Independent Quantum Key Distribution (MDI QKD) system has been implemented here in Bristol (Semenenko, 2020). To build on this result and work towards improved security and key rates, a new indium phosphide (InP) transmitter chip has been designed for a second-generation MDI QKD implementation. The new chip contains two laser sources, including a distributed feedback laser to allow for faster pulsing and high-speed phase modulators with a bandwidth of up to 30 GHz. With the new lasers and phase modulators a higher pulse rate will be achieved, leading to better key rates. Additionally, an on-chip photodiode can be used to monitor incoming light. This makes the chip much more resilient against hacking attacks, such as a Trojan Horse or Laser Damage Attacks. Since MDI QKD is intrinsically protected against detector attacks, this means that this new MDI QKD system will show great security overall.