Our work demonstrates the feasibility of complex ion-shuttling sequences combined with quantum logic, without the need to cool the ions during the computational sequence. We show that errors occurring throughout the in-sequence measurement are reliably detected, and therefore spurious computation results can be avoided. To reduce errors, ion qubits are moved within the trap structure during the computation. Our hardware platform is based on trapped atomic ions stored in a microchip ion trap, which consists of several independently controllable trapping zones. Here, we demonstrate a fault-tolerant version of a parity-measurement operation on a set of data quantum bits, which is a key building block of any quantum error correction protocol. But care must be taken that these operations do not act in a detrimental manner, as they are faulty themselves. Protocols for quantum error correction, consisting of repeated measurements and corrections, have been developed to mitigate these problems. However, their realization is hampered by the fact that their operation is inherently faulty. Quantum computers promise to solve computational tasks that are intractable for any existing computer. These architectural features in combination with the demonstrated approach to flag-based fault-tolerant quantum error correction open up a route toward scalable fault-tolerant quantum computing.
#Trapped ion quantum error correction full
The qubit register is dynamically reconfigured via shuttling operations enabling effective full connectivity without operational cross talk, thereby providing key prerequisites underlying fault-tolerant circuit design. Our hardware platform is based on atomic ions stored in a microchip ion trap.
The demonstrated fault-tolerant parity measurement scheme constitutes the key building block in a broad class of resource-efficient flag-based quantum error correction protocols including topological color codes. For holistic benchmarking of the parity measurement scheme, we use an entanglement witnessing scheme requiring a minimal number of measurements to verify genuine six-qubit multipartite entanglement. We show that the protocol is capable of reliably intercepting faults by deliberately injecting bit- and phase-flip errors. We achieve a parity measurement fidelity of 92.3(2)%, which increases to 93.2(2)% upon conditioning to the flag readout result, which shows that the measurement scheme intercepts intrinsic errors occurring throughout the sequence. We experimentally demonstrate a fault-tolerant weight-4 parity-check measurement scheme, where one additional flag qubit serves to detect errors, which would otherwise proliferate into uncorrectable weight-2 errors onto the qubit register. Recently, a paradigm requiring only minimal resource overhead in the form of “flag” qubits to detect and correct errors has been proposed. As these operations are inherently faulty, fault-tolerant schemes for realizing quantum error correction are required. Quantum error correction requires the detection of errors via reliable measurements of multiqubit correlation operators.
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