Researchers at the University of Innsbruck have achieved a significant advancement in quantum networking by successfully entangling ten individual qubits with separate photons. This breakthrough, detailed in Physical Review Letters, showcases a scalable method for connecting quantum processors, a crucial step towards building a functional quantum internet.
The team, led by Ben Lanyon, utilized a chain of ten calcium ions within a prototype quantum computer. Through precise manipulation of electric fields, each ion was directed into an optical cavity. A laser pulse then triggered the emission of a single photon, entangling the photon's polarization with the quantum state of its associated ion. This process generated a continuous stream of photons, each intrinsically linked to a distinct ion-qubit. This innovative technique demonstrated an impressive average ion-photon entanglement fidelity of 92%, highlighting its reliability and robustness.
A key strength of this method, as noted by Lanyon, is its inherent scalability. While previous experiments managed to link only a few ion-qubits to individual photons, this setup can be extended to much larger registers, potentially encompassing hundreds of ions. This scalability is fundamental for interconnecting quantum processors across greater distances, enabling more complex and distributed quantum applications.
The implications of this research extend beyond quantum networking itself. The technology also holds promise for enhancing the precision of optical atomic clocks. By linking these highly accurate clocks via quantum networks, it could pave the way for a global timekeeping system with unparalleled accuracy, benefiting fields like GPS navigation and telecommunications.
This advancement is a critical development for the future of quantum technologies, supported by funding from the Austrian Science Fund FWF and the European Union. It is part of a broader global effort to develop quantum networks, seen as the next evolution of the internet. Unlike classical networks that transmit data in bits, quantum networks use photons to carry quantum information, offering enhanced security and processing capabilities. Projects like Cisco's Quantum Network Entanglement Chip aim to build foundational infrastructure for the quantum internet, potentially accelerating the realization of practical quantum computing applications within the next decade. The University of Innsbruck's work contributes significantly to this burgeoning field, demonstrating a viable path towards creating larger, more complex quantum networks that could span continents.
Ben Lanyon, a Senior Scientist at IQOQI Innsbruck, is a leading figure in this research, focusing on novel approaches to build quantum networks and hybrid quantum systems. His team's work is part of the Quantum Internet Alliance, an international project under the EU Quantum Flagship, and builds upon previous demonstrations of quantum repeater nodes for telecommunication wavelengths.