Deterministic and scalable all-optical quantum computing using lithium niobate photonic integrated circuits

Quantum information science has emerged over the past decades to investigate whether new functionality and power can be gained by storing, processing and transmitting information encoded in quantum mechanical systems. The main obstacle for the practical realization of quantum information processing (QIP) is decoherence of the quantum bit (qubit) state due to interactions with its environment. As opposed to all other systems used for QIP, single photons are largely free of decoherence. While single photons can be easily manipulated to realize one-qubit logic gates, the major difficulty for optical quantum computing is in realizing deterministic two-qubit quantum gates required for universal quantum computation, because photons do not easily interact with each other. A second issue (which not only holds for photon-based QIP) is the scalability of the suggested approach in order to allow volume production, as well as realize more complex quantum circuits. In order to tackle these two major issues we will investigate erbium doped lithium niobate photonic integrated circuits (LN PICs). Such LN PICs are now available with high-index contrast and high quality, allowing dense integration and scalability. LN is moreover a good host for erbium dopants, which can mediate the interaction between photons to realize an optical two-qubit gate. As such, all functionalities for deterministic optical quantum computing could be realized on a monolithic and scalable platform.