Quantum computing aims to harness unique quantum effects to achieve capabilities beyond the reach of classical machines. Realizing this vision at scale requires fragile quantum information to be protected from noise. Unfortunately, only a limited set of operations can be implemented with fault tolerance, and many of them can already be efficiently simulated on a classical computer. Fortunately, this limitation can be overcome with what is known as quantum magic. This is a property of certain quantum states that enables operations outside the fault-tolerant, classically accessible set. Without this magic, even a perfectly error-corrected quantum computer would be no more powerful than a classical one. Quantifying magic is therefore essential for determining computational power, but doing so is challenging, especially for large many-body systems where complexity grows rapidly. Last year, Lorenzo Leone and Lennart Bittel of the Free University of Berlin showed theoretically that so-called stabilizer entropies offer a rigorous and experimentally accessible “meter” for magic [1]. Their analysis answered a long-standing question of how to reliably measure this resource, which is essential for realizing a universal quantum computer.
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