LAUSR

Quantum systems can be used to measure various quantities in their environment with high precision. Often, however, their sensitivity is limited by the decohering effects of this same environment. Dynamical decoupling schemes are widely used to filter environmental noise from signals, but their performance is limited by the spectral properties of the signal and noise at hand. Quantum error correction schemes have therefore emerged as a complementary technique without the same limitations. To date, however, they have failed to correct the dominant noise type in many quantum sensors, which couples to each qubit in a sensor in the same way as the signal. Here we show how quantum error correction can correct for such noise, which dynamical decoupling can only partially address. Whereas dynamical decoupling exploits temporal noise correlations in signal and noise, our scheme exploits spatial correlations. We give explicit examples in small quantum devices and demonstrate a method by which error-correcting codes can be tailored to their noise.Quantum sensing: Filtering noise using quantum error correctionNoise that couples to quantum sensors in the same way as the signal can be suppressed by exploiting spatial correlations. Adapting quantum error correction schemes into quantum sensing protocols can remove the effects of noise if the noise and the signal affect the sensor qubit differently. However, in most cases the dominant noise sources do not meet this condition. Paola Cappellaro and David Layden from the Massachusetts Institute of Technology have shown how to overcome this using qubits at different positions to construct an error corrected device. The noise correlations between the qubit sites provide additional structure that allows a successful error correction scheme. The achievable gain depends strongly on the nature of the noise and implementation, but earlier experimental results have found evidence for the necessary strong correlations in several experimental platforms.