The pursuit of practical quantum computers hinges on overcoming the challenge of connecting and controlling large numbers of qubits, the fundamental units of quantum information. Kai-Chi and colleagues at Delft University of Technology demonstrate a significant step towards this goal by achieving the quantum teleportation of a fundamental quantum gate, the controlled-NOT (CNOT) gate, within a silicon nanophotonic chip. This breakthrough represents the first demonstration of its kind, enabling remote quantum operations using only local control and classical communication, and paving the way for scalable, modular quantum computers. The team’s implementation achieves high-fidelity gate operation and successful remote entanglement creation, bringing fault-tolerant, large-scale distributed quantum computation closer to reality.
Quantum Gate Teleportation on a Chip
Quantum Leap for Distributed Computing: Teleporting Quantum Gates on a Chip Researchers have achieved a significant milestone in the development of large-scale quantum computers by successfully demonstrating the teleportation of a quantum gate between remote qubits on a single chip. This breakthrough addresses a critical challenge in building practical quantum computers, scaling up the number of qubits and connecting them reliably. Instead of physically connecting distant qubits, this approach uses the principles of quantum teleportation to transfer information and perform operations remotely, paving the way for modular quantum architectures. The team focused on building a system where quantum information can be processed in localized modules and then shared through entanglement, a uniquely quantum connection.
Traditional methods struggle with direct interactions between distant qubits, but quantum teleportation offers a solution by leveraging shared entanglement, local operations, and classical communication. This allows for the execution of quantum operations between qubits without a direct physical link, effectively “teleporting” the gate operation itself. The researchers implemented this by creating a system where a controlled-NOT (CNOT) gate, a fundamental building block of quantum computation, could be transferred between qubits on a silicon chip. The experiment involved creating entangled pairs of photons and then using these to establish a quantum link between two modules on the chip.
By performing specific local operations and utilizing classical communication, the team successfully teleported a CNOT gate from one pair of qubits to another. The teleported gate achieved a remarkably high truth table fidelity of 93. 1%, demonstrating the precision and reliability of the process. Furthermore, the quantum state fidelity, which measures how accurately the quantum information is transferred, reached 87. 0%, a level sufficient for complex computations.
This achievement represents a substantial improvement over existing methods, which often suffer from signal loss and errors when attempting to connect distant qubits. The researchers also demonstrated the ability to create entanglement between four qubits remotely, with a fidelity of 86. 2%, showcasing the potential for building larger, more complex quantum networks. The overall quantum process fidelity reached 83. 1%, and the non-local CNOT gate fidelity was 86.
This work opens exciting possibilities for building distributed quantum computers, where multiple modules can be connected via optical fibers to create a powerful, scalable system. By overcoming the limitations of direct qubit connections, this technology brings us closer to realizing the full potential of quantum computation and unlocking solutions to currently intractable problems. This implementation offers a pathway to modular quantum computing, where smaller, specialised components are linked together to create a more powerful system.
The team also demonstrated the creation of remote entanglement between qubits, achieving an average fidelity of 86. 2% for generating logical Bell states. While acknowledging current limitations, the authors highlight potential improvements through deterministic schemes, entanglement purification, and non-destructive measurement techniques. Future work will focus on extending this technology to multiple chip-scale modules and exploring the telecommunication band for remote entanglement, ultimately aiming for a scalable and fault-tolerant modular quantum computer based on photonic qubits.