Scientists have created an “extraordinarily bright” light source that can generate quantum entangled photons (particles of light) that could be used to securely transmit data in a future high-speed quantum communications network.
A future quantum internet could store information about pairs of entangled Photons – that is, the particles share information across time and space, regardless of distance. Based on the strange laws of Quantum mechanicsInformation encoded in these entangled photons can be transmitted at high speed, while their “quantum coherence” – a state in which the particles are entangled – ensures that the data cannot be intercepted.
However, one of the biggest challenges in building a quantum internet was that the strength of these photons can decrease the farther they travel; the light sources were not bright enough. To build a successful quantum internet that can send data over long distances, the photons must be strong enough to prevent “decoherence” – where the entanglement is lost and the information they contain disappears.
In a study published on July 24 in the journal eLightScientists from Europe, Asia and South America have created a novel quantum signal source using existing technologies that achieves extremely high brightness.
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They achieved this by combining a photon point emitter (a generator of single photons or particles of light) with a quantum resonator (a device for amplifying the quantum signature) to create the powerful new quantum signal.
What makes the current research particularly interesting is that although the individual technologies have been independently tested in laboratories, they have only been tested separately. This study is the first time that they have been used in combination.
The researchers combined the photon point emitter with a circular Bragg resonator (a reflector used to guide electromagnetic waves) on a piezoelectric actuator (a device that generates electricity when heated or stressed). Together, they created an improved form of photon emitter that allows the emitted photons to be fine-tuned for maximum polarized entanglement. This was controlled using the piezoelectric actuator.
The photon pairs produced by the device exhibited high entanglement fidelity and extraction efficiency – that is, each photon is bright enough to be useful and retains its “quantum signature” (a useful quantum property) well. Until now, achieving a useful level of brightness and high entanglement fidelity at the same time has been difficult because each aspect required a different technology and these were difficult to combine in a scalable way.
This represents a significant advance in the development of practical quantum technologies and shows how these can be combined to create a more powerful and practical light source.
Unfortunately, it is not expected that a quantum internet will be available any time soon, as the various technologies are still in the experimental and development phase. The production of the photon emitter used in the study also required toxic raw materials such as arsenic, which had to be handled in a special way. There are also safety concerns with the use of gallium arsenide, from which the photon point emitter was made. Fisher Scientifica supplier of laboratory equipment and chemicals for scientific research, Lists Gallium arsenide is considered dangerous for several reasons, including its carcinogenic properties.
The safety concerns associated with the use of these materials could limit the scalability of the described method, so there may be a need to identify viable alternative materials to generate bright, entangled photons for future quantum communication networks.
The next development step is to integrate a diode-like structure onto the piezoelectric actuator. This would make it possible to generate an electric field across the quantum dots to counteract decoherence and thus increase the degree of entanglement.
Although many more steps are needed to develop a quantum internet, the successful combination of a photon emitter and a resonator to produce high-brightness, entangled photons is still a significant advance, the scientists said.
