Driven Quantum Dynamics: Will It Blend?

“Random number generation plays a pivotal role in quantum information applications (such as encryption), but generating random quantum operations requires exceptionally complex resources. A new theoretical analysis shows that an interacting many-body system can blend classical randomness through its dynamics to create quantum randomness.”



Random number generators play a prominent role in many technologies such as cryptography, computer science, and numerical computation algorithms (such as the ubiquitous Monte Carlo methods). Within quantum information science, random quantum operations have found a similar pivotal role in applications such as quantum encryption, noise estimation, and demonstrating quantum supremacy. Unfortunately, creating quantum randomness is much harder than creating its classical analog. Quantum algorithms that can generate truly random or pseudorandom operations require quantum devices as complex as a universal quantum computer, far exceeding the capability of any current technology. On the other hand, nature already provides us with complex quantum systems, namely, many-body systems. Such systems are central to condensed-matter physics and quantum simulation but are incapable of creating randomness on their own. We pose the following key question: If we provide a many-body system with classical randomness through driving, then does it efficiently blend it into quantum randomness via its natural dynamics? We find that this is, indeed, sometimes true.
More precisely, we show that whenever the mean-field approximation is valid, then the system scrambles efficiently. We also provide an example for which the scrambling is inefficient (which implies that mean-field theory is invalid for this model). Finally, we provide an integrable model of experimental interest, for which the efficiency is provably true.
Our results show that some quantum many-body systems can also be used as “quantum blenders.”

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