Any Orthonormal Basis in High Dimension is Uniformly Distributed over the Sphere

TL;DR

This paper demonstrates that any orthonormal basis in a high-dimensional Hilbert space appears uniformly distributed over the sphere when tested with randomized partitions, with implications for quantum statistical mechanics.

Contribution

It proves that orthonormal bases in high dimensions pass randomized uniformity tests with high probability, linking geometric properties to quantum mechanics applications.

Findings

Orthonormal bases in high dimensions are nearly uniformly distributed over the sphere.

Randomized partition tests effectively identify uniform distribution of bases.

Application to quantum statistical mechanics is briefly discussed.

Abstract

Let X be a real or complex Hilbert space of finite but large dimension d, let S(X) denote the unit sphere of X, and let u denote the normalized uniform measure on S(X). For a finite subset B of S(X), we may test whether it is approximately uniformly distributed over the sphere by choosing a partition A_1,...,A_m of S(X) and checking whether the fraction of points in B that lie in A_k is close to u(A_k) for each k=1,...,m. We show that if B is any orthonormal basis of X and m is not too large, then, if we randomize the test by applying a random rotation to the sets A_1,...,A_m, B will pass the random test with probability close to 1. This statement is related to, but not entailed by, the law of large numbers. An application of this fact in quantum statistical mechanics is briefly described.