A Fully Pipelined Architecture of Quantum-Classical Interface for Realizing Fault-Tolerant Quantum Computer

We propose a fully pipelined Quantum-Classical interface (QC-IF) architecture for fault-tolerant quantum computing. The current Quantum-Classical interface has been working for superconducting quantum computers with 64 qubits in RIKEN and 16 qubits in QIQB Osaka University. The interface sends/receives a sequence of pulses to/from the qubits and demodulates the acquired ones, in which a batch controller is designed to operate up to 500 milliseconds, longer than the coherence time. For Fault-Tolerant Quantum Computers(FTQC), however, a fully pipelined Quantum-Classical Interface is required to send and receive pulses, collecting syndrome information over time far beyond the coherence time. Here, we present a control plane newly incorporated into the current architecture to handle consecutive sending, receiving, and demodulating pulses. Since the current system has achieved wire-rate operation to retrieve and transmit signals, the control plane for continuous operation naturally extends the system to a fully pipelined architecture.