Scientists have demonstrated a powerful technique that will allow quantum computers to store much more information in photons of light. The team managed to encode eight levels of data into photons and read it back easily, representing an exponential leap over previous systems.
Traditional computers store and process information in binary bits, which can hold a value of zero or one. Quantum computers boost this power drastically with their quantum bits, or qubits, which can hold values of zero, one or both at the same time. But an emerging version of qubits, known as qudits, up the game even more. Rather than just two values like qubits, qudits can theoretically contain dozens of different values, greatly increasing the data processing and storage potential. Better yet, qudits are also more resilient against external noise that can disrupt qubits.
But, of course, there’s a catch: it’s hard to measure and read back data stored on qudits. So for the new study, researchers at Oak Ridge National Laboratory, Purdue University and EPFL have developed a technique to produce and read qudits more reliably. In their experiments, they generated qudits that could each hold up to eight levels of information, and quantum-entangled them in pairs to generate a 64-dimensional quantum space. This, the team says, is four times larger than in previous studies.
The experiments start by shining a laser into a micro-ring resonator, which is a small circular structure that produces pairs of photons with eight-dimensional states. The color frequencies of these pairs are entangled, producing a quantum space that can theoretically hold up to 64 values of data.
The researchers used an electro-optic phase modulator to mix the different frequencies of light in different ways, then a pulse shaper modified the phase of these frequencies. These instruments are already often used in telecommunications, but in this case, the team performed the operations at random. This generates many different types of frequency correlations, which the scientists then analyzed using statistical methods and simulations to find the ones that would work best for quantum information systems.
In future experiments, the team plans to send these entangled photons down optical fibers to test things like quantum teleportation and entanglement swapping, which will be useful protocols for quantum communication.
The research was published in the journal Nature Communications.
Source: Oak Ridge