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Current communications using optical fibres encode information using a binary system with only two options – 1 or 0, on or off, A or B, red or blue. Now, EU-funded scientists have developed technology to encode information in single photons, taking advantage of quantum properties across a much broader spectrum of options. The ground-breaking research has potential applications in ultrafast and secure communication, quantum computing and quantum-enhanced metrology and sensing.
Using this new approach, photons are not just red or blue, but can be both at the same time and many colours in between: in effect, data can be written into photons using an alphabet of rainbows.
The research conducted in the QCUMbER project addresses key challenges of optical communications, enabling much more data to be squeezed into light particles, or photons.
‘We developed a complete toolbox for quantum light pulses, which allowed us to generate, manipulate and measure tailored quantum rainbows,’ says project coordinator Brian Smith at the University of Oxford in the United Kingdom.
‘Using this toolbox, we succeeded in demonstrating ultra-precise detectors with a resolution that surpasses the capabilities of standard detectors, quantum communication with an alphabet that goes beyond the standard binary encoding used today, and quantum information processing, where we could build large quantum states comprising many entangled rainbows. These proof-of-concept applications are the precursor for future quantum technologies based on quantum light pulses.’
Encoding and decoding rainbows
The QCUMbER researchers also explored applications for quantum entanglement, described by Einstein as 'spooky action at a distance'. The mysterious and logic-defying phenomenon occurs when two quantum particles form a strongly linked pair and the state of one defines the state of the other, no matter how far apart they are. By controlling the link between the entangled particles, scientists could create ultra-secure methods of communication and ultra-powerful computing technologies far beyond anything conceivable today.
While such applications remain theoretical for now, other quantum properties of the photons explored in QCUMbER are set to have a more immediate impact on research and industry.
‘The QCUMbER project has brought the two areas of ultrashort light pulses and quantum light to the fore as an important and new approach to harness quantum optical fields for enhanced applications and research,’ Smith says.
A key breakthrough was the ability to single out one of many quantum rainbows, enabling encoded photons to be detected and interpreted accurately as a means of communication.
‘We achieved this with several complementary approaches, based on either special detectors, “rainbow filters” if you like, that will see only one user-defined pulse, or tailored quantum pulse gates that route one user-chosen pulse to a different output channel. These techniques allow, for instance, the decoding of information that is spelled out with quantum rainbows,’ Smith says.
New drug development
In addition, novel high-precision metrology techniques are being enabled by harnessing the quantum properties of photons for extremely accurate measurements at any scale, driving the broader development of ultra-precise quantum-enhanced sensing technologies. Structures built with many linked quantum particles could also be used to simulate complex chemical processes, aiding for example the development of new drugs and chemical compounds.
‘Results from the project demonstrated a quantum advantage in sensing chemical reactions,’ Smith says. ‘Beyond this, the project established new metrics for quantifying the non-classicality or “quantumness” of a light field. Many of these results are supporting continued research by the project partners and have been taken up by others in the broader quantum information science community.’
Some of the partners are now applying for additional funding in order to build on the results of the QCUMbER project.