Prospects for quantum computing: Extremely doubtful
Prospects for quantum computing: Extremely doubtful
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量子计算的前景：极其令人怀疑
DOI：
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发表时间：
2014
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影响因子：
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通讯作者：
Mikhail I. Dyakonov
中科院分区：
文献类型：
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作者：
Mikhail I. Dyakonov
量子计算机应该通过对定义N个量子比特状态的2N个复振幅应用幺正变换来处理信息。一台有用的机器需要N~103或更多，描述量子计算机在任何给定时刻状态的连续参数的数量至少为21000 ~10300，这比宇宙中质子的数量要大得多。然而，理论家们认为，大规模量子计算的可行性已经通过“阈值定理”得到了证明。像任何定理一样，证明是基于一些被认为是公理的假设。然而，在物理世界中，这些假设都不能完全实现。任何假设都只能以有限的精确度进行处理。因此，毫无意义的“每门每量子比特的误差”阈值必须由一系列精确度来补充，这些精确度是阈值定理背后的所有假设都应该成立的。这样一份名单仍然不存在。该理论似乎也忽略了量子计算机不受欢迎的自由演化，这是由进入任何给定叠加态的量子态的能量差引起的。另一个重要的观点是，假设的量子计算机将是一个103 - 106量子比特的系统，加上一个极其复杂和极其复杂的经典设备。这个巨大的强非线性系统通常会表现出不稳定性和混沌行为。
The quantum computer is supposed to process information by applying unitary transformations to 2N complex amplitudes defining the state of N qubits. A useful machine needing N~103 or more, the number of continuous parameters describing the state of a quantum computer at any given moment is at least 21000 ~10300 which is much greater than the number of protons in the Universe. However, the theorists believe that the feasibility of large-scale quantum computing has been proved via the “threshold theorem”. Like for any theorem, the proof is based on a number of assumptions considered as axioms. However, in the physical world none of these assumptions can be fulfilled exactly. Any assumption can be only approached with some limited precision. So, the rather meaningless “error per qubit per gate” threshold must be supplemented by a list of the precisions with which all assumptions behind the threshold theorem should hold. Such a list still does not exist. The theory also seems to ignore the undesired free evolution of the quantum computer caused by the energy differences of quantum states entering any given superposition. Another important point is that the hypothetical quantum computer will be a system of 103 –106 qubits PLUS an extremely complex and monstrously sophisticated classical apparatus. This huge and strongly nonlinear system will generally exhibit instabilities and chaotic behavior.