M. Iuliano
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Quantum Internet: a step closer
Demonstrations and Applications using Diamond Qubits
In the hardware framework, the Nitrogen-Vacancy center in diamond represents a viable platform as processing end node, thanks to the high quality of its qubits and the capability of generating remote entanglement with other nodes in the network via its optical interface. These properties can be engineered to utilize the NV center as a test-bed for demonstrating crucial steps towards the Quantum Internet final goal.
We first employ a two-node NV quantum network in the laboratory to demonstrate the elementary building-blocks of distributed quantum computation: the generation of a distributed 4-partite Greenberger-Horne-Zeilinger state and the realization of a non-local Controlled-NOT gate between physically separated and non-interacting qubits.
In the long distance scenario, we use the NV center platform to study the photonic interface of solid-state qubits with time-bin qubits compatible with the emission from quantum memory platforms, such as Rubidium gas or Thulium-doped crystals. The interface is benchmarked with a quantum teleportation experiment. Quantum teleportation is the ultimate protocol that enables the transfer of quantum information from one physical point to another. We teleport a photonic time-bin qubit to the communication qubit of the NV center platform, establishing the primary form of communication between heterogeneous platforms in a quantum network.
Finally, the two-node NV network is used as reliable setup to demonstrate the first operating system for quantum network applications, QNodeOS. QNodeOS can schedule and manage quantum network applications in a multitasking fashion. It constitutes a software interface which enables facilitated access for users, boosting the research in quantum network applications and making a first step towards the deployment of such technology into society. ...
In the hardware framework, the Nitrogen-Vacancy center in diamond represents a viable platform as processing end node, thanks to the high quality of its qubits and the capability of generating remote entanglement with other nodes in the network via its optical interface. These properties can be engineered to utilize the NV center as a test-bed for demonstrating crucial steps towards the Quantum Internet final goal.
We first employ a two-node NV quantum network in the laboratory to demonstrate the elementary building-blocks of distributed quantum computation: the generation of a distributed 4-partite Greenberger-Horne-Zeilinger state and the realization of a non-local Controlled-NOT gate between physically separated and non-interacting qubits.
In the long distance scenario, we use the NV center platform to study the photonic interface of solid-state qubits with time-bin qubits compatible with the emission from quantum memory platforms, such as Rubidium gas or Thulium-doped crystals. The interface is benchmarked with a quantum teleportation experiment. Quantum teleportation is the ultimate protocol that enables the transfer of quantum information from one physical point to another. We teleport a photonic time-bin qubit to the communication qubit of the NV center platform, establishing the primary form of communication between heterogeneous platforms in a quantum network.
Finally, the two-node NV network is used as reliable setup to demonstrate the first operating system for quantum network applications, QNodeOS. QNodeOS can schedule and manage quantum network applications in a multitasking fashion. It constitutes a software interface which enables facilitated access for users, boosting the research in quantum network applications and making a first step towards the deployment of such technology into society.
Quantum networks connecting quantum processing nodes via photonic links enable distributed and modular quantum computation. In this framework, quantum gates between remote qubits can be realized using quantum teleportation protocols. The essential requirements for such non-local gates are remote entanglement, local quantum logic within each processor, and classical communication between nodes to perform operations based on measurement outcomes. Here, we demonstrate an unconditional Controlled-NOT quantum gate between remote diamond-based qubit devices. The control and target qubits are Carbon-13 nuclear spins, while NV electron spins enable local logic, readout, and remote entanglement generation. We benchmark the system by creating a Greenberger-Horne-Zeilinger state, showing genuine 4-partite entanglement shared between nodes. Using deterministic logic, single-shot readout, and real-time feed-forward, we implement non-local gates without post-selection. These results demonstrate a key capability for solid-state quantum networks, enabling exploration of distributed quantum computing and testing of complex network protocols on full-stack systems.
Solid-state quantum registers consisting of optically active electron spins with nearby nuclear spins are promising building blocks for future quantum technologies. For electron spin-1 registers, dynamical decoupling (DD) quantum gates have been developed that enable the precise control of multiple nuclear spin qubits. However, for the important class of electron spin-1/2 systems, this control method suffers from intrinsic selectivity limitations, resulting in reduced nuclear spin gate fidelities. Here, we demonstrate improved control of single nuclear spins by an electron spin-1/2 using dynamically decoupled radio-frequency (DDRF) gates. We make use of the electron spin-1/2 of a diamond tin-vacancy center, showing high-fidelity single-qubit gates, single-shot readout, and spin coherence beyond a millisecond. The DD control is used as a benchmark to observe and control a single 31C nuclear spin. Using the DDRF control method, we demonstrate improved control on that spin. In addition, we find and control an additional nuclear spin that is insensitive to the DD control method. Using these DDRF gates, we show entanglement between the electron and the nuclear spin with 72(3)% state fidelity. Our extensive simulations indicate that DDRF gate fidelities well in excess are feasible. Finally, we employ time-resolved photon detection during readout to quantify the hyperfine coupling for the electron's optically excited state. Our work provides key insights into the challenges and opportunities for nuclear spin control in electron spin-1/2 systems, opening the door to multiqubit experiments on these promising qubit platforms.
We demonstrate large-range tuning of the optical transition of Tin-Vacancies (SnV) in diamond using electro-mechanical-induced strain, realizing >40 GHz tuning. We employ real-time feedback on the strain environment to stabilize the resonant frequency.
The negatively charged tin-vacancy (SnV−) center in diamond has emerged as a promising platform for quantum computing and quantum networks. To connect SnV− qubits in large networks, in situ tuning and stabilization of their optical transitions are essential to overcome static and dynamic frequency offsets induced by the local environment. Here, we report on the large-range optical frequency tuning of diamond SnV− centers using micro-electro-mechanically mediated strain control in photonic integrated waveguide devices. We realize a tuning range of >40 GHz, covering a major part of the inhomogeneous distribution. In addition, we employ real-time feedback on the strain environment to stabilize the resonance frequency and mitigate spectral wandering. These results provide a path for on-chip scaling of diamond SnV-based quantum networks.