In July 2017, China launched the world’s first quantum messaging and file sharing service, and now researchers from the Ohio State University, Duke University and Oak Ridge National Laboratory have come up a new system that creates and transmits quantum keys up to 10 times faster than existing technology.
There has been many advancements in quantum computing, especially in the last decade, and soon this may give hackers access to the machines that are powerful enough to break even the strongest security standards of the internet. This means, all bank transactions, passwords and crucial data on the servers would be vulnerable to attack.
To take care of these kinds of future threats, scientists are working to implement the same advanced quantum technology to make system theoretically hack proof, using quantum data encryption. Till date, they have achieved a milestone of distributing quantum encryption code at the rate of one megabit per second.
Problem With Existing System
The Quantum Key Distribution (QKD) works on one of the basic properties of quantum mechanics – analyzing a single matter like proton or electron changes its properties. In security system, this feature could be used to instantly alert both authorized sender and receiver about the security breach.
The concept of QKD is not new, it was first introduced in 1984, and now large-scale applications are being implemented in the real world. For example, China transferred a quantum key between two ground stations located 1,200 kilometers apart, via a satellite. A few European companies have started selling laser based system for QKD.
However, one of the main limitations with these systems is that they send keys at slow speed, between 10 to 100 kilobits per second. At these rates, the systems cannot be used for practical application like video streaming or a telephone call.
The New Level of Quantum Cryptography
The secret behind the high speed transmission lies in putting more data in photons of light and combining it with high-speed detectors that feature over 70% of detection efficiency and less than 40 picosecond of jitter.
This is achieved by tunning the photon’s property called phase, and the time at which photons are released. This allowed scientist to encode 2 bits of data in each photon, instead of just 1.
Then, pairing these photons with high-speed detectors allowed their system to send encoded data 5 to 10 times faster than other techniques. Multiple systems using this technique are runned parallely to produce current internet speeds that are fast enough to host a telephone conversation or low-quality video streaming.
Is it Completely Secure?
In an ideal scenario, any attempt to breach security would leave transmission errors, which could be effortlessly detected by the receiver and the sender. However, in the real world we don’t have perfect equipment, and this might open some loopholes that attackers can exploit.
The scientists thoroughly analyzed the shortcomings of all devices they used in the experiment. They worked to incorporate these defects into the theory in order to make sure that the system is safe.
All components used in the experiment are available in the market, except single photon detectors. The photons can be transferred through optical fiber cables, making it quite easy to integrate their equipments (like transmitter and receiver) into existing infrastructure. Also, it could be extended to free-space quantum channels.
According to researchers, with some modification, the whole system can be made to fit in a regular CPU-sized box. The demonstrated method is robust against coherent attacks, and wide range of experimental imperfections are detected in the system.
Experimental Setup and Technical Details
The quantum photonic states are generated by frequency stabilized continuous laser, operating at 1,550 nanometers. It goes through a phase modulator and 3 intensity modulators. The complete setup is controlled by serial pattern generator (designed with field programmable gate array), operating at a clock rate of 10 GHz.
Reference: ScienceAdvance research article: QKD with time-bin qudits
A sine wave generator phase locked to field programmable gate array (FPGA), operating at 5 GHz rate, drives an intensity modulator that generates periodic optical pulses of 66 picoseconds. These optical pulses goes through an intensity modulator (labelled as IM 1 in the figure), which is driven by field programmable gate array pattern generator, in order to define the data pattern for either phase states or time-bin.
Driven by independent field programmable gate array channel, the 2nd intensity modulator (IM 2) is responsible for adjusting the amplitude of phase as well as decoy states. Eventually, it goes through a phase modulator (PM), which is also driven by field programmable gate array, for encoding different phase states.
The phase basis and time-bin basis are selected with probabilities of 0.1 and 0.9. The attenuator (ATT) is attached to decrease the states level to single-photon level. One more attenuator can be used to simulate the quantum channel loss.
At the receiver end, the incoming signals are divided by a beam splitter that directs 10% of the states to the phase basis system and 90% to the temporal basis measurement system. The superconducting nanowire single-photon detectors are used for both measurement bases. The detections are captured with 50 picosecond resolution time to digital converter, which is synced with receiver’s clock over a public channel.