Abstract
AbstractExperimentalists seeking to improve the coherent lifetimes of quantum bits have generally focused on mitigating decoherence mechanisms through, for example, improvements to qubit designs and materials, and system isolation from environmental perturbations. In the case of the phase degree of freedom in a quantum superposition, however, the coherence that must be preserved is not solely internal to the qubit, but rather necessarily includes that of the qubit relative to the ‘master clock’ (e.g., a local oscillator) that governs its control system. In this manuscript, we articulate the impact of instabilities in the master clock on qubit phase coherence and provide tools to calculate the contributions to qubit error arising from these processes. We first connect standard oscillator phase-noise metrics to their corresponding qubit dephasing spectral densities. We then use representative lab-grade and performance-grade oscillator specifications to calculate operational fidelity bounds on trapped-ion and superconducting qubits with relatively slow and fast operation times. We discuss the relevance of these bounds for quantum error correction in contemporary experiments and future large-scale quantum information systems, and consider potential means to improve master clock stability.
Highlights
A fundamental challenge to the broad application of quantum information science is the management of error in fragile quantum hardware.[1,2] The need for higher fidelity performance motivates research at all architectural levels,[3] from theoretical studies of fault tolerance and analyses of quantum error correction (QEC) implementations down to experimental improvements in the operational fidelity of elemental devices
The calculations we have presented demonstrate that master clock phase fluctuations are an emerging consideration for quantum information applications
On the other hand, using high-performance precision local oscillator (LO), the calculated error rates for ^l and X^ operations with both the fast and slow gates considered here are at several orders of magnitude smaller than the current state-of-art (Table 1)
Summary
A fundamental challenge to the broad application of quantum information science is the management of error in fragile quantum hardware.[1,2] The need for higher fidelity performance motivates research at all architectural levels,[3] from theoretical studies of fault tolerance and analyses of quantum error correction (QEC) implementations down to experimental improvements in the operational fidelity of elemental devices. Such controls generally constitute time-dependent modulation of the system dynamics with the aim of coherently averaging out slow fluctuations These protocols have typically been saturation phenomenology observed in precision oscillator characterisation.[20] associated with the mitigation of environmental decoherence, For both free evolution and driven operations, the deleterious as the reader might expect based on the discussion above in impact of using a LO increases as the duration of the operation ‘Qubit dephasing induced by the master clock’, a growing body of literature has shown that errors induced by imperfect control—. The plateau-like behaviour in infidelity with increasing floor; even if LO hardware were improved, we could do no evolution time is due to the interplay of the dephasing power spectrum and filter-function,[50] and is similar to phase-error better than saturating the thermal noise floor across the control bandwidth This is generically quoted as − 174 dBm/Hz for a npj Quantum Information (2016) 16033. Noise at higher frequencies evolves too rapidly to be coherently averaged by the control, resulting in the filter transfer functions for the DES
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
