Abstract
To implement fault-tolerant quantum computation with continuous variables, the Gottesman-Kitaev-Preskill (GKP) qubit has been recognized as an important technological element. However,it is still challenging to experimentally generate the GKP qubit with the required squeezing level, 14.8 dB, of the existing fault-tolerant quantum computation. To reduce this requirement, we propose a high-threshold fault-tolerant quantum computation with GKP qubits using topologically protected measurement-based quantum computation with the surface code. By harnessing analog information contained in the GKP qubits, we apply analog quantum error correction to the surface code.Furthermore, we develop a method to prevent the squeezing level from decreasing during the construction of the large scale cluster states for the topologically protected measurement based quantum computation. We numerically show that the required squeezing level can be relaxed to less than 10 dB, which is within the reach of the current experimental technology. Hence, this work can considerably alleviate this experimental requirement and take a step closer to the realization of large scale quantum computation.
Highlights
Quantum computation has a great deal of potential to efficiently solve some hard problems for conventional computers [1,2]
We have proposed a high-threshold fault-tolerant quantum computation (FTQC) to alleviate the required squeezing level for CV-FTQC by harnessing analog information contained in the GKP qubits
The proposed method consists of applying analog quantum error correcting (QEC) to the surface code and constructing the cluster state for the topologically protected measurement-based quantum computation (MBQC) with a low error accumulation by using the postselected measurement
Summary
Quantum computation has a great deal of potential to efficiently solve some hard problems for conventional computers [1,2]. The required squeezing level in the existing CV-FTQC scheme [12], combined with the fault-tolerant scheme with the threshold 0.67 × 10−2 [27], is 16.0 dB [28] This improvement results from the reduction from 16.0 dB to 9.8 dB, which corresponds to the reduction of the error probability to misidentify the single GKP qubit in q and p quadrature from 2.7 × 10−15 to 7.4 × 10−5. By achieving the requirement of the squeezing level around 10 dB, we believe this work can take a considerable step closer to the realization of large-scale quantum computation with digitized CV states and will be indispensable to construct CV-FTQC.
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