Encoding a magic state with beyond break-even fidelity.

To run large-scale algorithms on a quantum computer, error-correcting codes must be able to perform a fundamental set of operations, called logic gates, while isolating the encoded information from noise1-8. We can complete a universal set of logic gates by producing special resources called magic states9-11. It is therefore important to produce high-fidelity magic states to conduct algorithms while introducing a minimal amount of noise to the computation. Here we propose and implement a scheme to prepare a magic state on a superconducting qubit array using error correction. We find that our scheme produces better magic states than those that can be prepared using the individual qubits of the device. This demonstrates a fundamental principle of fault-tolerant quantum computing12, namely, that we can use error correction to improve the quality of logic gates with noisy qubits. Moreover, we show that the yield of magic states can be increased using adaptive circuits, in which the circuit elements are changed depending on the outcome of mid-circuit measurements. This demonstrates an essential capability needed for many error-correction subroutines. We believe that our prototype will be invaluable in the future as it can reduce the number of physical qubits needed to produce high-fidelity magic states in large-scale quantum-computing architectures.

High threshold error correction for the surface code.

An algorithm is presented for error correction in the surface code quantum memory. This is shown to correct depolarizing noise up to a threshold error rate of 18.5%, exceeding previous results and coming close to the upper bound of 18.9%. The time complexity of the algorithm is found to be polynomial with error suppression, allowing efficient error correction for codes of realistic sizes.

Bringing order through disorder: localization of errors in topological quantum memories.

Anderson localization emerges in quantum systems when randomized parameters cause the exponential suppression of motion. Here we consider this phenomenon in topological models and establish its usefulness for protecting topologically encoded quantum information. For concreteness we employ the toric code. It is known that in the absence of a magnetic field this can tolerate a finite initial density of anyonic errors, but in the presence of a field anyonic quantum walks are induced and the tolerable density becomes zero. However, if the disorder inherent in the code is taken into account, we demonstrate that the induced localization allows the topological quantum memory to regain a finite critical anyon density and the memory to remain stable for arbitrarily long times. We anticipate that disorder inherent in any physical realization of topological systems will help to strengthen the fault tolerance of quantum memories.

Needle guide in shoulder arthroscopy - a technique.

Distension of joint with fluid is often used to facilitate insertion of arthroscope. This may prove difficult at times in the shoulder joint, as unlike the knee, it is deeply situated, making extravasation of fluid outside the capsule, a common occurrence. This is especially true in very tight joints and is often a problem for beginners. We describe here a very effective and simple technique where a needle is used to distend the shoulder before the insertion of the arthroscope.

Loose Metasul liner causing partial amputation of the neck of the femoral component.

The use of metal-on-metal bearings in total hip arthroplasty is becoming increasingly popular. Several authors have reported excellent medium- and long-term results after the use of the Metasul metal-on-metal articulation (Sulzer Medica, Winterthur, Switzerland). We report a case of a loose Metasul liner eroding the neck of the femoral component resulting in extensive metallosis and weakening of the prosthesis.