Resolving Matrix Spencer Conjecture Up to Poly-logarithmic Rank

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Publication:6408645

DOI10.1145/3564246.3585103arXiv2208.11286MaRDI QIDQ6408645

Raghu Meka, Haotian Jiang, Nikhil Bansal

Publication date: 23 August 2022

Abstract: We give a simple proof of the matrix Spencer conjecture up to poly-logarithmic rank: given symmetric dimesd matrices A1,ldots,An each with |Ai|mathsfopleq1 and rank at most n/log3n, one can efficiently find pm1 signs x1,ldots,xn such that their signed sum has spectral norm |sumi=1nxiAi|mathsfop=O(sqrtn). This result also implies a lognOmega(loglogn) qubit lower bound for quantum random access codes encoding n classical bits with advantage gg1/sqrtn. Our proof uses the recent refinement of the non-commutative Khintchine inequality in [Bandeira, Boedihardjo, van Handel, 2022] for random matrices with correlated Gaussian entries.







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