Mapping a 50-spin-qubit network through correlated sensing

Spins associated to optically accessible solid-state defects have emerged as a versatile platform for exploring quantum simulation, quantum sensing and quantum communication. Pioneering experiments have shown the sensing, imaging, and control of multiple nuclear spins surrounding a single electron spin defect. However, the accessible size of these spin networks has been constrained by the spectral resolution of current methods. Here, we map a network of 50 coupled spins through high-resolution correlated sensing schemes, using a single nitrogen-vacancy center in diamond. We develop concatenated double-resonance sequences that identify spin-chains through the network. These chains reveal the characteristic spin frequencies and their interconnections with high spectral resolution, and can be fused together to map out the network. Our results provide new opportunities for quantum simulations by increasing the number of available spin qubits. Additionally, our methods might find applications in nano-scale imaging of complex spin systems external to the host crystal.

Mid-circuit correction of correlated phase errors using an array of spectator qubits

Scaling up invariably error-prone quantum processors is a formidable challenge. Although quantum error correction ultimately promises fault-tolerant operation, the required qubit overhead and error thresholds are daunting. In a complementary proposal, co-located, auxiliary 'spectator' qubits act as in-situ probes of noise, and enable real-time, coherent corrections of data qubit errors. We use an array of cesium spectator qubits to correct correlated phase errors on an array of rubidium data qubits. By combining in-sequence readout, data processing, and feed-forward operations, these correlated errors are suppressed within the execution of the quantum circuit. The protocol is broadly applicable to quantum information platforms, and establishes key tools for scaling neutral-atom quantum processors: mid-circuit readout of atom arrays, real-time processing and feed-forward, and coherent mid-circuit reloading of atomic qubits.

Fault-tolerant operation of a logical qubit in a diamond quantum processor

Solid-state spin qubits is a promising platform for quantum computation and quantum networks^1,2. Recent experiments have demonstrated high-quality control over multi-qubit systems^3–8, elementary quantum algorithms^8–11 and non-fault-tolerant error correction^12–14. Large-scale systems will require using error-corrected logical qubits that are operated fault tolerantly, so that reliable computation becomes possible despite noisy operations^15–18. Overcoming imperfections in this way remains an important outstanding challenge for quantum science^15,19–27. Here, we demonstrate fault-tolerant operations on a logical qubit using spin qubits in diamond. Our approach is based on the five-qubit code with a recently discovered flag protocol that enables fault tolerance using a total of seven qubits^28–30. We encode the logical qubit using a new protocol based on repeated multi-qubit measurements and show that it outperforms non-fault-tolerant encoding schemes. We then fault-tolerantly manipulate the logical qubit through a complete set of single-qubit Clifford gates. Finally, we demonstrate flagged stabilizer measurements with real-time processing of the outcomes. Such measurements are a primitive for fault-tolerant quantum error correction. Although future improvements in fidelity and the number of qubits will be required to suppress logical error rates below the physical error rates, our realization of fault-tolerant protocols on the logical-qubit level is a key step towards quantum information processing based on solid-state spins.

By using a five-qubit error-correcting code with a recently discovered flag protocol, a logical qubit that is operated fault-tolerantly is realized based on solid-state spin qubits in diamond.

Many-body-localized discrete time crystal with a programmable spin-based quantum simulator

[Figure: see text].

Orbital and Spin Dynamics of Single Neutrally-Charged Nitrogen-Vacancy Centers in Diamond

The neutral charge state plays an important role in quantum information and sensing applications based on nitrogen-vacancy centers. However, the orbital and spin dynamics remain unexplored. Here, we use resonant excitation of single centers to directly reveal the fine structure, enabling selective addressing of spin-orbit states. Through pump-probe experiments, we find the orbital relaxation time (430 ns at 4.7 K) and measure its temperature dependence up to 11.8 K. Finally, we reveal the spin relaxation time (1.5 s) and realize projective high-fidelity single-shot readout of the spin state (≥98%).

Associations between the Drug Burden Index, Potentially Inappropriate Medications and Quality of Life in Residential Aged Care

BACKGROUND

Inappropriate polypharmacy may negatively impact the quality of life of residents in aged care facilities, but it remains unclear which medications may influence this reduced quality of life.

OBJECTIVE

The objective of this study was to examine whether the Drug Burden Index and potentially inappropriate medications were associated with quality of life in older adults living in residential care with a high prevalence of cognitive impairment and dementia.

METHODS

We conducted cross-sectional analyses of 541 individuals recruited from 17 residential aged care facilities in Australia in the Investigating Services Provided in the Residential Environment for Dementia (INSPIRED) study. Quality of life was measured using the EuroQol Five Dimensions Questionnaire (a measure of generic quality of life) and the Dementia Quality of Life Questionnaire completed by the participant or a proxy.

RESULTS

In the 100 days prior to recruitment, 83.1% of the participants received at least one anticholinergic or sedative medication included in the Drug Burden Index and 73.0% received at least one potentially inappropriate medication according to the Beers Criteria. Multi-level linear models showed there was a significant association between a higher Drug Burden Index and lower quality of life according to the EuroQol Five Dimensions Questionnaire [β (standard error): - 0.034 (0.012), p = 0.006] after adjustment for potential confounding factors. Increasing numbers of potentially inappropriate medications were also associated with lower EuroQol Five Dimensions Questionnaire scores [- 0.030 (0.010), p = 0.003] and Dementia Quality of Life Questionnaire-Self-Report-Utility scores [- 0.020 (0.009), p = 0.029]. Exposure to both Drug Burden Index-associated medications and potentially inappropriate medications was associated with lower Dementia Quality of Life Questionnaire-Self-Report-Utility scores [- 0.034 (0.017), p = 0.049].

CONCLUSION

Exposure to anticholinergic and sedative medications and potentially inappropriate medications occurred in over three-quarters of a population of older adults in residential care and was associated with a lower quality of life.