  Quantum computers are expected to bring drastic acceleration to several
computing tasks against classical computers. Noisy intermediate-scale quantum
(NISQ) devices, which have tens to hundreds of noisy physical qubits, are
gradually becoming available, but it is still challenging to achieve useful
quantum advantages in meaningful tasks at this moment. On the other hand, the
full fault-tolerant quantum computing (FTQC) based on the quantum error
correction (QEC) code remains far beyond realization due to its extremely large
requirement of high-precision physical qubits. In this study, we propose a
quantum computing architecture to close the gap between NISQ and FTQC. Our
architecture is based on erroneous arbitrary rotation gates and error-corrected
Clifford gates implemented by lattice surgery. We omit the typical distillation
protocol to achieve direct analog rotations and small qubit requirements, and
minimize the remnant errors of the rotations by a carefully-designed state
injection protocol. Our estimation based on numerical simulations shows that,
for early-FTQC devices that consist of $10^4$ physical qubits with physical
error probability $p = 10^{-4}$, we can perform roughly $1.72 \times 10^7$
Clifford operations and $3.75 \times 10^4$ arbitrary rotations on 64 logical
qubits. Such computations cannot be realized by the existing NISQ and FTQC
architectures on the same device, as well as classical computers. We hope that
our proposal and the corresponding development of quantum algorithms based on
it bring new insights on realization of practical quantum computers in future.
