Tunable light looks for the perfect qubit

One of the most promising candidates for the perfect quantum qubit are defect centres in solid-state materials, also known as colour centres, which have been found to emit a single photon per excitation event when excited by laser light of a particular frequency. An important technique for characterising these colour centers is photoluminescence excitation (PLE) spectroscopy, which measures the tiny optical signals produced by single-photon emitters when they are excited by continuous-wave (cw) laser light. Widely tuneable cw lasers based on OPO technology make it quicker and easier to characterise the internal energy structure of different qubit contenders. This white paper presents such a suitable tuneable cw laser source, outlining the advantages and illustrating examples of how this laser can be used to characterise novel colour centers.