Decades of expertise in the field of integrated silicon photonics technology at CEA-Leti supports the development of key state-of-the-art quantum photonic components on-chip. These building blocks are then employed to create advanced photonic integrated circuits for applications such as quantum communications and computing.
leti-cea.com, Nov. 26, 2024 –
Quantum computers employ quantum bits (qubits) and once mature, these ultra-powerful machines will be able to solve extremely complex problems far beyond existing capabilities. Generating and managing qubits, however, is a major scientific and engineering challenge. Amongst the multiple physical carriers currently explored as potential qubits, photons are one promising approach. "CEA-Leti advances research on both semiconductor and photonic qubits," explains Ségolène Olivier, Integrated Quantum Photonics Program Manager.
"Though this work is currently carried out in parallel, there will certainly be meeting points in the future: the architecture of quantum processors will likely be distributed in networks and optical quantum communications will be required to link the different processors together whatever their nature."
Optical quantum communications will also be necessary to provide the increased security required once quantum computers become a reality.
"Quantum computers threaten the security of current communication systems, in particular classical encryption protocols for the transfer of sensitive information between locations," explains Olivier. "Quantum cryptography ensures ultra-secure data transmission through advanced quantum-encryption protocols whereby the cryptographic keys needed to encrypt and decrypt data are encoded and transmitted using photonic qubits in the form of single photons."
State-of-the-art integrated components for the generation, manipulation and detection of photonic qubits are the essential building blocks needed to produce advanced silicon photonics technology for these quantum applications. Heralded single-photon source technology via a nonlinear process of entangled photon pair generation has been developed at CEA-Leti, enabling the achievement of a high generation rate of photon pairs.
"The generation rate needs to be as high as possible for quantum communication or computing applications," explains Olivier.
A generation rate in the MHz range, i.e. a few million photon pairs per second, was demonstrated in 2019. A more advanced architecture design enabled a significant improvement of the source technology leading to the achievement of a GHz generation rate on-chip in 2023. The optimization of these GHz sources continues; first to ensure high efficiency coupling of the emitted photon pairs into fibers for the transmission of quantum encryption keys. The second development involves harnessing the multiple degrees of freedom of photons to encode several qubits per photon pair – referred to as hyper-entanglement – for more efficient quantum communication schemes.
Development has also focused on ultrasensitive detectors, capable of detecting the arrival of a single photon.