Lasers Eyed as Way Forward for Quantum Encryption of Data, Cryptocurrencies

Researchers at the University of Southern California have developed a technology called a frequency comb that could pave the way for quantum-encryption technologies to be used to protect mobile data and digital currencies.

Given yesterday’s news that cryptocurrencies remain in the crosshairs of hackers, people would surely welcome new methods to secure them. Researchers at the University of Southern California (USC) think they’ve found just that: using pulses of light for data encryption.

The technique, which involves the use of a tool called a “frequency comb” advances quantum encryption and could be used to protect Bitcoin and other digital currencies, according to a team of researchers led by Professor Andrea Armani at the USC Viterbi School of Engineering.

The team invented the frequency comb, which converts a single wavelength into multiple wavelengths into tens or hundreds of lasers from a single laser in a size and with an efficiency that paves the way for its use in next-generation quantum encryption technologies.

Nanomaterials make for more scalable technology

Frequency comb technologies already exist, but they are typically large, sometimes as big as a refrigerator, and require significant amounts of power to operate. The tool developed by the USC team solves these problems through the use of nanomaterials—specifically, carbon-based, organic molecules—making it the size of a human hair, researchers said.

By applying only a single layer of a 25-atom organic molecule to the surface of a laser, the comb developed by the team required 1000 times less power to operate than typical technologies. This allows for mobile as well as a wider range of other applications, said Armani, chair in Engineering and Material Sciences at USC’s Viterbi School.

“Organic optical materials have already transformed the electronics industry, leading to lighter, lower-power TVs and cellphone displays, but previous attempts to directly interface these materials with lasers stumbled,” she said in an article on the USC website. “We solved the interface challenge. Because our approach can be applied to a wide range of organic materials and laser types, the future possibilities are very exciting.”

Image of organic-molecule enhanced frequency comb (Credit: Vinh Diep and Alexa Hudnut, USC)

The initial applications for frequency combs are to detect trace amounts of chemicals and to keep high-precision time. However, scientists are beginning to explore their use in quantum cryptography, which is how security researchers can apply the USC team’s invention in new data- and cryptocurrency-security technologies, Armani said.

Current means of data encryption basically lock data in a digital envelope, with some locks—just like physical ones—being easier to break than others. While current encryption methods focus on creating more complex and dynamic locks, security researchers have found themselves limited in how to detect when encryption has failed.

That’s where quantum encryption can present an alternative approach, not only implementing more complex means to encrypt data, but also to detect immediate intrusion through changes in the transmitted data signal, researchers said.

Enabling more possibilities for quantum cryptography

Frequency combs can enable a phenomenon called proton entanglement, a leading method of quantum cryptography researchers are eyeing. In this method, researchers must create entangled pairs of photons exactly the same time with exactly the same properties. While it sounds virtually impossible, it’s not—thanks to frequency combs, they said.

The performance of frequency combs depends on the two wavelengths generated by the technology’s primary laser having different energy levels—one higher and one lower. Additionally, these energies must in total be exactly equal to the primary laser as well as appear at exactly the same time.

In essence, then, frequency-comb generators also are entangled-photon generators, researchers said. This makes them an ideal technology for use in quantum-encryption techniques.

With its invention, the USC team has tackled the technical hurdles of reducing the size and power requirements of frequency combs to use quantum cryptography on portable platforms to secure data, Armani said. However, researchers face integration and manufacturing challenges before these technologies are ready for prime time, she said.

To read more about the technology and its potential uses in depth, check out a paper published by the researchers in the journal Science Advances.

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