The Gottesman–Kitaev–Preskill encoding of a qubit in a harmonic oscillator is a promising building block towards fault-tolerant quantum computation. Recently, this encoding was experimentally demonstrated for the first time in trapped-ion and superconducting circuit systems. However, these systems lack some of the Gaussian operations which are critical to efficiently manipulate the encoded qubits. In particular, homodyne detection, which is the go-to method for efficient readout of the encoded qubit in the vast majority of theoretical work, is not readily available, heavily limiting the readout fidelity. Here, we present an alternative read-out strategy designed for qubit-coupled systems. Our method can improve the readout fidelity with several orders of magnitude for such systems and, surprisingly, even surpass the fidelity of homodyne detection in the low squeezing regime.

谐波振荡器中量子位的 Gottesman-Kitaev-Preskill 编码是实现容错量子计算的有前途的构建块。最近，这种编码首次在俘获离子和超导电路系统中得到了实验证明。然而，这些系统缺乏一些对有效操纵编码量子位至关重要的高斯运算。特别是零差检测，这是绝大多数理论工作中有效读出编码量子位的首选方法，不容易获得，严重限制了读出保真度。在这里，我们提出了一种为量子位耦合系统设计的替代读出策略。我们的方法可以将此类系统的读出保真度提高几个数量级，而且令人惊讶的是，