Abstract
Quantum resetting protocols allow a quantum system to be sent to a state in the past by making it interact with quantum probes when neither the free evolution of the system nor the interaction is controlled. We experimentally verify the simplest non-trivial case of a quantum resetting protocol, known as the {{mathcal{W}}}_{4} protocol, with five superconducting qubits, testing it with different types of free evolutions and target–probe interactions. After projection, we obtained a reset state fidelity as high as 0.951, and the process fidelity was found to be 0.792. We also implemented 100 randomly chosen interactions and demonstrated an average success probability of 0.323 for left|1rightrangle and 0.292 for left|-rightrangle, and experimentally confirmed the nonzero probability of success for unknown interactions; the numerical simulated values are about 0.3. Our experiment shows that the simplest quantum resetting protocol can be implemented with current technologies, making such protocols a valuable tool in the eternal fight against unwanted evolution in quantum systems.
Highlights
The tug of war between the natural but unknown evolution of a quantum system and control mechanisms to correct error introduced by such evolution is one of the most important technical challenges in the implementation of reliable quantum computers
We divide the circuit into four parts: state preparation, free evolution, interaction, and tomographic readout
The first probe interacts with the target via a bipartite unitary operator U, which varies according to the experimental case. This process of free evolution followed by target–probe interaction is repeated three more times on the target and different probes
Summary
The tug of war between the natural but unknown evolution of a quantum system and control mechanisms to correct error introduced by such evolution is one of the most important technical challenges in the implementation of reliable quantum computers. A more recent technique[6] constructs a universal quantum circuit to probabilistically implement the exact inverse evolution of some quantum gate when only the dimension of the target and the number of permitted uses of the gate are known. These techniques, rely on very different assumptions. 6 is exact, with a realistic probability of success which increases exponentially with the number of uses allowed for the gate to be inverted It does not directly remove an evolution, since the inverted gate must be subsequently applied to the target
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