Quantum computers may offer significant computational advantages over classical counterparts, revolutionizing the technology landscape in the near future. When networked together, the advantage of quantum computing may be further amplified, and there may emerge innovative applications. Among various active explorations on distributed quantum computing, multiqubit quantum gates between distant networked quantum computers are of particular interest because they offer operational advantages of efficiency and fidelity. Here we report the first experimental demonstration of quantum teleportation for a Toffoli gate, which is a commonly used multiqubit quantum gate, across three spatially distributed parties within a photonic quantum network. Employing the Hofmann method, we estimate the fidelity of the teleported Toffoli gate to be at least 0.706 ± 0.131. This successful demonstration of the quantum teleportation of a Toffoli gate constitutes a critical step toward the ultimate realization of distributed quantum computation.
Quantum computers may offer significant computational advantages over classical counterparts, revolutionizing the technology landscape in the near future. When networked together, the advantage of quantum computing may be further amplified, and there may emerge innovative applications. Among various active explorations on distributed quantum computing, multiqubit quantum gates between distant networked quantum computers are of particular interest because they offer operational advantages of efficiency and fidelity. Here we report the first experimental demonstration of quantum teleportation for a Toffoli gate, which is a commonly used multiqubit quantum gate, across three spatially distributed parties within a photonic quantum network. Employing the Hofmann method, we estimate the fidelity of the teleported Toffoli gate to be at least 0.706 ± 0.131. This successful demonstration of the quantum teleportation of a Toffoli gate constitutes a critical step toward the ultimate realization of distributed quantum computation.
Teleportation of unitary operations can be viewed as a quantum remote control. The remote realization of robust multiqubit logic gates among distant long-lived qubit registers is a key challenge for quantum computation and quantum information processing. Here we propose a simple and deterministic scheme for teleportation of a Toffoli gate among three spatially separated electron spin qubits in optical microcavities by using local linear optical operations, an auxiliary electron spin, two circularly-polarized entangled photon pairs, photon measurements, and classical communication. We assess the feasibility of the scheme and show that the scheme can be achieved with high average fidelity under the current technology. The scheme opens promising perspectives for constructing long-distance quantum communication and quantum computation networks with solid-state qubits.
Abstract Distributed quantum computing (DQC) combines the computing power of multiple networked quantum processing modules, ideally enabling the execution of large quantum circuits without compromising performance or qubit connectivity 1,2 . Photonic networks are well suited as a versatile and reconfigurable interconnect layer for DQC; remote entanglement shared between matter qubits across the network enables all-to-all logical connectivity through quantum gate teleportation (QGT) 3,4 . For a scalable DQC architecture, the QGT implementation must be deterministic and repeatable; until now, no demonstration has satisfied these requirements. Here we experimentally demonstrate the distribution of quantum computations between two photonically interconnected trapped-ion modules. The modules, separated by about two metres, each contain dedicated network and circuit qubits. By using heralded remote entanglement between the network qubits, we deterministically teleport a controlled-Z (CZ) gate between two circuit qubits in separate modules, achieving 86% fidelity. We then execute Grover’s search algorithm 5 —to our knowledge, the first implementation of a distributed quantum algorithm comprising several non-local two-qubit gates—and measure a 71% success rate. Furthermore, we implement distributed iSWAP and SWAP circuits, compiled with two and three instances of QGT, respectively, demonstrating the ability to distribute arbitrary two-qubit operations 6 . As photons can be interfaced with a variety of systems, the versatile DQC architecture demonstrated here provides a viable pathway towards large-scale quantum computing for a range of physical platforms.
We implement the gate teleportation algorithm for teleporting arbitrary two-qubit Clifford gates and the Toffoli gate within the context of multi-node quantum networks, utilizing the SquidASM quantum network simulator. We show how a gate teleportation scheme can be used to implement gate cutting, which is an important approach to realize large circuits in distributed quantum computing environments. The correction operations in teleportation are automatically constructed for arbitrary two-qubit Clifford gates. We apply a similar gate teleportation protocol for the Toffoli gate, but the correction operation becomes more complex since the gate is non-Clifford. We present the simulation results for the CNOT, DCNOT, CZ, SWAP, and Toffoli gates. We perform the simulations under varying quantum channel and device noise levels. The simulations provide valuable insights into the robustness and efficacy of the implemented algorithms, and they assist in identifying the critical components within quantum networks where noise primarily affects the execution of applications.
Abstract Teleportation of an unknown quantum operation, implementing a nonlocal gate on two distant particles, constitutes a fundamental component in quantum networks and distributed large‐scale quantum computers. In this study, it is realized that the experimental demonstration of teleporting photon‐photon diagonal block operations. Assisted by two previously shared entangled photons, a local photon‐photon diagonal block operation is transferred to its corresponding nonlocal gate and the protocol is able to realize a nonlocal photon–photon operation with diagonal block forms containing two unknown single‐qubit unitary operations. In experiment, two nonlocal diagonal block operations are successfully implemented on two separated independent single photons: the controlled‐NOT (CNOT) gate and the controlled‐Z (CZ) gate. To characterize the performance of the nonlocal photon–photon operations, the quantum teleported process fidelity is estimated. Additionally, the entangling capability of teleported photon–photon CNOT gate is verified. These results provide an approach to implement a unknown nonlocal photon–photon diagonal block gate and may have broad applications in distributed quantum information processing including quantum communication and quantum computation.
Future quantum networks require efficient quantum state and gate teleportation as key interfacing capabilities. However, many physical systems naturally host high-dimensional quantum states that cannot be seamlessly interfaced with standard qubit-based quantum systems. Two- and high-dimensional quantum systems are expected to complement each other in future quantum computing tasks, and quantum networks capable of realizing high- and cross-dimensional quantum gate teleportation are critical to unlocking this potential. In this work, we first propose a generalized high- and cross-dimensional quantum gate teleportation protocol and then experimentally verify it on a programmable silicon-photonic chip. The eight qubit–ququart cross-dimensional Bell states achieved via gate teleportation exhibit an average fidelity of 0.965±0.021, while the average process fidelities for the three teleported qubit–ququart quantum gates range from 0.893±0.007 to 0.941±0.005. The results lay the foundation for integrating high-dimensional quantum states and gates into future quantum networks.
Abstract Future quantum internet applications will derive their power from the ability to share quantum information across the network1,2. Quantum teleportation allows for the reliable transfer of quantum information between distant nodes, even in the presence of highly lossy network connections3. Although many experimental demonstrations have been performed on different quantum network platforms4–10, moving beyond directly connected nodes has, so far, been hindered by the demanding requirements on the pre-shared remote entanglement, joint qubit readout and coherence times. Here we realize quantum teleportation between remote, non-neighbouring nodes in a quantum network. The network uses three optically connected nodes based on solid-state spin qubits. The teleporter is prepared by establishing remote entanglement on the two links, followed by entanglement swapping on the middle node and storage in a memory qubit. We demonstrate that, once successful preparation of the teleporter is heralded, arbitrary qubit states can be teleported with fidelity above the classical bound, even with unit efficiency. These results are enabled by key innovations in the qubit readout procedure, active memory qubit protection during entanglement generation and tailored heralding that reduces remote entanglement infidelities. Our work demonstrates a prime building block for future quantum networks and opens the door to exploring teleportation-based multi-node protocols and applications2,11–13.