University of Queensland
Research Field: Quantum photonics, Quantum information
Dr Romero works in quantum photonics: encoding information in the quantum properties of light. If we use the polarisation of light that has two levels, we have a quantum alphabet of two letters–qubits. She is exploring using the transverse shape of light, which has more levels, allowing for many more letters–qudits. This enables incredibly compact messaging: e.g., encoding 1000 words with qubits requires 32 photons; encoding the same 1000 words with 10-level qudits requires only 2 photons.
In addition, since the encoded information is quantum, it exhibits bizarre—but useful!—properties. Using the shape of photons, she has demonstrated entanglement—arguably the most curious quantum phenomenon—in which information is shared between spatially separated particles. The conclusion from such experiments is that quantum objects have indefinite properties, unlike a red ball which is always a red ball regardless of whether someone is looking at it or not. Recently, she has shown that the order of events can be indefinite: “A is before B”, and “B is before A” can be simultaneously true in quantum physics. These phenomena are more than mere curiosities, with potential applications in securely transmitting information and tackling otherwise impossible problems.