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%).

Ozone Formation in Photochemical Oxidation of Organic Substances

The formation of ozone through photochemical oxidation of alcohols, aldehydes, ketones, acids, and hydrocarbons, such as are present in gasoline, in the presence of small quantities of nitrogen oxides has been demonstrated. Ozone production without the addition of nitrogen oxides has been observed in the photochemical oxidation of biacetyl, bibutyryl, pyruvic acid, and butyl nitrite. The ozone produced in these reactions was identified by chemical and physical methods. The ozone formation is attributed to a peroxide radical chain reaction. The release of large quantities of hydrocarbons to the air and the simultaneous presence of nitrogen oxides from combustion processes explains the relatively high ozone content, and consequent severe rubber cracking, in the Los Angeles area. These findings should be considered in planning rubber storage facilities. In view of the irritating properties of the products formed by this photochemical oxidation, both hydrocarbons and nitrogen oxides should be considered as potential irritants when they occur simultaneously in the air at low concentrations.

The Application of Rubber in the Quantitative Determination of Ozone

A convenient rubber cracking test for ozone is described. This method serves not only as a rapid, positive means of identifying ozone in complex gas mixtures but also gives close approximation to the quantity present. Application of the method in determining ozone in heavy smog atmosphere is shown. The high ozone concentration in these tests is attributed to ozone formation under the catalytic action of nitrogen oxides and sunlight.

The Effect of Temperature on the Sunlight Deterioration of a Rubber Compound

The subject of this article might be the question: “Does temperature have an effect on the deterioration of rubber in sunlight and, if so, approximately how much effect?” We are interested in any effect of temperature because rubber goods in service are frequently subjected to sunlight over a fairly wide temperature range. There are apparently very few references or comments in the literature on this subject; but we wish to look briefly at some significant experiments of the past which have to do with sunlight without regard for temperature, and then discuss a new experiment.