Most boson quantum states are almost maximally entangled

<p>The geometric measure of entanglement <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper E"> <mml:semantics> <mml:mi>E</mml:mi> <mml:annotation encoding="application/x-tex">E</mml:annotation> </mml:semantics> </mml:math> </inline-formula> of an <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="m"> <mml:semantics> <mml:mi>m</mml:mi> <mml:annotation encoding="application/x-tex">m</mml:annotation> </mml:semantics> </mml:math> </inline-formula> qubit quantum state has maximum value bounded above by <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="m"> <mml:semantics> <mml:mi>m</mml:mi> <mml:annotation encoding="application/x-tex">m</mml:annotation> </mml:semantics> </mml:math> </inline-formula>. In previous work of Gross, Flammia, and Eisert, it was shown that <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper E greater-than-or-equal-to m minus upper O left-parenthesis log m right-parenthesis"> <mml:semantics> <mml:mrow> <mml:mi>E</mml:mi> <mml:mo>≥<!-- ≥ --></mml:mo> <mml:mi>m</mml:mi> <mml:mo>−<!-- − --></mml:mo> <mml:mi>O</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>log</mml:mi> <mml:mo>⁡<!-- ⁡ --></mml:mo> <mml:mi>m</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:annotation encoding="application/x-tex">E \ge m-O(\log m)</mml:annotation> </mml:semantics> </mml:math> </inline-formula> with high probability as <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="m right-arrow normal infinity"> <mml:semantics> <mml:mrow> <mml:mi>m</mml:mi> <mml:mo stretchy="false">→<!-- → --></mml:mo> <mml:mi mathvariant="normal">∞<!-- ∞ --></mml:mi> </mml:mrow> <mml:annotation encoding="application/x-tex">m\to \infty</mml:annotation> </mml:semantics> </mml:math> </inline-formula>. They showed, as a consequence, that the vast majority of states are too entangled to be computationally useful. In this paper, we show that for <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="m"> <mml:semantics> <mml:mi>m</mml:mi> <mml:annotation encoding="application/x-tex">m</mml:annotation> </mml:semantics> </mml:math> </inline-formula> qubit <italic>Boson</italic> quantum states, the maximal possible geometric measure of entanglement is bounded above by <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="log Subscript 2 Baseline m"> <mml:semantics> <mml:mrow> <mml:msub> <mml:mi>log</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mspace width="negativethinmathspace" /> <mml:mi>m</mml:mi> </mml:mrow> <mml:annotation encoding="application/x-tex">\log _2\! m</mml:annotation> </mml:semantics> </mml:math> </inline-formula>, opening the door to many computationally universal states. We further show the corresponding concentration result that <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper E greater-than-or-equal-to log Subscript 2 Baseline m minus upper O left-parenthesis log log m right-parenthesis"> <mml:semantics> <mml:mrow> <mml:mi>E</mml:mi> <mml:mo>≥<!-- ≥ --></mml:mo> <mml:msub> <mml:mi>log</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mspace width="negativethinmathspace" /> <mml:mi>m</mml:mi> <mml:mo>−<!-- − --></mml:mo> <mml:mi>O</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>log</mml:mi> <mml:mo>⁡<!-- ⁡ --></mml:mo> <mml:mi>log</mml:mi> <mml:mo>⁡<!-- ⁡ --></mml:mo> <mml:mi>m</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:annotation encoding="application/x-tex">E \ge \log _2\! m - O(\log \log m)</mml:annotation> </mml:semantics> </mml:math> </inline-formula> with high probability as <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="m right-arrow normal infinity"> <mml:semantics> <mml:mrow> <mml:mi>m</mml:mi> <mml:mo stretchy="false">→<!-- → --></mml:mo> <mml:mi mathvariant="normal">∞<!-- ∞ --></mml:mi> </mml:mrow> <mml:annotation encoding="application/x-tex">m\to \infty</mml:annotation> </mml:semantics> </mml:math> </inline-formula>. We extend these results also to <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="m"> <mml:semantics> <mml:mi>m</mml:mi> <mml:annotation encoding="application/x-tex">m</mml:annotation> </mml:semantics> </mml:math> </inline-formula>-mode <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="n"> <mml:semantics> <mml:mi>n</mml:mi> <mml:annotation encoding="application/x-tex">n</mml:annotation> </mml:semantics> </mml:math> </inline-formula>-bit Boson quantum states.</p>

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