17 July 2018
Totally secure data transfer could be possible, claim researchers from the University of Sheffield.
The team explain they have managed to generate very rapid single-photon light pulses, with each photon representing a bit of binary code.
According to the researchers, these photons cannot be intercepted without disturbing them in a way that would alert the sender that something was amiss.
Data transfer using light passed along fibre optic cables is common practice, but with each pulse containing millions of photons, a portion could be intercepted without detection.
Secure data is already encrypted, but if an ‘eavesdropper’ was able to intercept the signals containing details of the code then – in theory – they could access and decode the rest of the message.
Single photon pulses offer total security because any eavesdropping is immediately detected. However, scientists have struggled to produce them rapidly enough to carry data at sufficient speeds to transfer high volumes of data.
The Sheffield team explain they employed a phenomenon called the ‘Purcell Effect’ to produce the photons very rapidly. A nanocrystal called a quantum dot is placed inside a cavity within a larger crystal – the semiconductor chip. The dot is then bombarded with light from a laser which makes it absorb energy. This energy is then emitted in the form of a photon.
Placing the nanocrystal inside a very small cavity makes the laser light bounce around inside the walls. This speeds up the photon production by the Purcell Effect. One problem is that the photons carrying data information can easily become confused with the laser light. The Sheffield researchers say they have overcome this by funnelling the photons away from the cavity and inside the chip to separate the two different types of pulse.
The team say they succeeded in making the photon emission rate approximately 50 times faster. Although this isn’t the fastest photon light pulse yet developed, it has a crucial advantage because the photons produced are all identical – an essential quality for many quantum computing applications.
Professor Mark Fox of the University of Sheffield, explains: “Using photons to transmit data enables us to use the fundamental laws of physics to guarantee security. It’s impossible to measure or ‘read’ the particle in any way without changing its properties. Interfering with it would therefore spoil the data and sound an alarm.
“This technology could be used within secure fibre optic telecoms systems, although it would be most useful initially in environments where security is paramount, including governments and national security headquarters.”
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