Efficient deterministic algorithms are proposed with logarithmic step complexities for the generation of entangled GHZN and WN states useful for quantum networks, and an implementation on the IBM quantum computer up to N=16 is demonstrated. Improved quality is then investigated using full quantum tomography for low‐N GHZ and W states. This is completed by parity oscillations and histogram distance for large‐N GHZ and W states, respectively. Robust states are built with about twice the number of quantum bits which were previously achieved.
Entanglement is a fundamental resource in quantum information and technology. In article number 1900015, Clément Javerzac‐Galy and co‐workers investigate efficient new algorithms to create N‐qubit Greenberger–Horne–Zeilinger (GHZ) and W states with time‐complexity scaling linearly and logarithmically in N. Quantum circuits are implemented on the IBM quantum computer up to N = 16, and entanglement is investigated through tomography (and other methods) as shown in the cover picture. While the fidelity decreases with increasing N, it does so more slowly for the logarithmic algorithms. (Image design by Chun Lam Chan.)
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