A research team comprising Filippo Miatto and other physicists from the University of Strathclyde, Glasgow, UK, has discovered a new technique to reliably evaluate the information carried by photon pairs utilized for quantum computing and cryptography applications.
The study results have been reported in European Physical Journal D. With these results, the information in the photon pairs can be accessed even if the measurements on them are defective. The researchers concentrated on photon pairs that are in a quantum entanglement state, specifically composed of several superimposed pairs of states. Thus, these photon pairs are closely connected by general physical properties such as orbital angular momentum, a spatial property that is capable of demonstrating different values for every superimposed state.
The researchers depended on a tool that can decompose the superimposed states of the photon pairs onto the various dimensions of a Hilbert space, a virtual space defined by mathematical equations. By this approach, they were able to understand the degree of entanglement of the photon pairs.
The research team demonstrated that the degree of accessibility of the information carried by the photon pairs is more when the degree of entanglement is higher. Thus, creating entangled photon pairs with a higher dimension, i.e., with an adequate amount of decomposed photon states that are measurable may be helpful in revealing their information with greater certainty.
This means that even a defective measurement of physical properties of photons does not impact the quantity of information that can be obtained if the degree of entanglement was originally robust. These results pave the way to quantum information applications with better error resilience and a greater information density coding per photon pair. They also enable cryptography applications where a less number of photons carry more information regarding complex quantum encryption keys.