dorsal/arxiv
View SchemaGeneral Phase Matching Condition for Quantum Searching
| Authors | Gui-Lu Long, Li Xiao, Yang Sun |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0107013 |
| URL | https://arxiv.org/abs/quant-ph/0107013 |
Abstract
We present a general phase matching condition for the quantum search algorithm with arbitrary unitary transformation and arbitrary phase rotations. We show by an explicit expression that the phase matching condition depends both on the unitary transformation U and the initial state. Assuming that the initial amplitude distribution is an arbitrary superposition sin\theta_0 |1> + cos\theta_0 e^{i\delta} |2> with |1> = {1 / sin\beta} \sum_k |\tau_k> <\tau_k|U|0> and |2> = {1 / cos\beta} \sum_{i \ne \tau}|i> <i|U|0>, where |\tau_k> is a marked state and \sin\beta = \sqrt{\sum_k|U_{\tau_k 0}|^2} is determined by the matrix elements of unitary transformation U between |\tau_k> and the |0> state, then the general phase matching condition is tan{\theta / 2} [cos 2\beta + tan\theta_0 cos\delta sin 2\beta]= tan{\phi / 2} [1-tan\theta_0 sin\delta sin 2\beta tan{\theta / 2}], where \theta and \phi are the phase rotation angles for |0> and |\tau_k>, respectively. This generalizes previous conclusions in which the dependence of phase matching condition on $U$ and the initial state has been disguised. We show that several phase conditions previously discussed in the literature are special cases of this general one, which clarifies the question of which condition should be regarded as exact.
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"date_created": "2026-03-02T18:01:45.341000Z",
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"abstract": "We present a general phase matching condition for the quantum search\nalgorithm with arbitrary unitary transformation and arbitrary phase rotations.\nWe show by an explicit expression that the phase matching condition depends\nboth on the unitary transformation U and the initial state. Assuming that the\ninitial amplitude distribution is an arbitrary superposition sin\\theta_0 |1\u003e +\ncos\\theta_0 e^{i\\delta} |2\u003e with |1\u003e = {1 / sin\\beta} \\sum_k |\\tau_k\u003e\n\u003c\\tau_k|U|0\u003e and |2\u003e = {1 / cos\\beta} \\sum_{i \\ne \\tau}|i\u003e \u003ci|U|0\u003e, where\n|\\tau_k\u003e is a marked state and \\sin\\beta = \\sqrt{\\sum_k|U_{\\tau_k 0}|^2} is\ndetermined by the matrix elements of unitary transformation U between |\\tau_k\u003e\nand the |0\u003e state, then the general phase matching condition is tan{\\theta / 2}\n[cos 2\\beta + tan\\theta_0 cos\\delta sin 2\\beta]= tan{\\phi / 2} [1-tan\\theta_0\nsin\\delta sin 2\\beta tan{\\theta / 2}], where \\theta and \\phi are the phase\nrotation angles for |0\u003e and |\\tau_k\u003e, respectively. This generalizes previous\nconclusions in which the dependence of phase matching condition on $U$ and the\ninitial state has been disguised. We show that several phase conditions\npreviously discussed in the literature are special cases of this general one,\nwhich clarifies the question of which condition should be regarded as exact.",
"arxiv_id": "quant-ph/0107013",
"authors": [
"Gui-Lu Long",
"Li Xiao",
"Yang Sun"
],
"categories": [
"quant-ph"
],
"title": "General Phase Matching Condition for Quantum Searching",
"url": "https://arxiv.org/abs/quant-ph/0107013"
},
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