{'fraction_non_alphanumeric': 0.021145807720678634, 'fraction_numerical': 0.0051635111876075735, 'mean_word_length': 4.964809384164223, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Gold nanowires to mend a heart Incorporating gold nanowires into porous alginate scaffolds can improve the conductivity of engineered heart patches made from these materials

whose spin encodes a qubit — from one quantum dot to another. In a conventional wire this electron would quickly be lost in a sea of other electrons. With this motivation, two research groups — Christopher Bäuerle and Tristan Meunier of the Institut Néel in Grenoble and coworkers at laboratories in France, Japan and Germany1, and independently, Chris Ford and co-workers at Cambridge University and the National Physical Laboratory2 — have demonstrated an alternative means of transportation for electrons. They still use a nanowire but dry up its electron sea, and then to help the electrons over the peaks in the potential, they employ an applied electrical potential as a nanoscale ‘conveyor belt’. This applied potential has many minima, and each of these is able to trap electrons. By changing the position of these minima it is possible to remove a single electron from a quantum dot, drag it along the nanowire (and over all the peaks in the potential inside the nanowire), and deposit it in a second quantum dot. In many ways the minima in the applied potential are like mobile quantum dots. This mechanism is already remarkably reliable, working for approximately 95% of attempted transfers1,2. This allowed Ford and co-workers2 to shuttle an electron back and forth between two quantum dots up to 60 times, which means that the cumulative distance travelled by the electron was about 0.25 mm — a distance that is almost macroscopic. The speed of the electron shuttle is remarkable: moving at 2,870 m s–1, it would be classified as ‘hypersonic’ if it were an airplane. Of course, most electrons in the electron sea move about a hundred times faster owing to the exclusion principle, so taking the shuttle must feel more like riding a camel than a jet. Nevertheless, the shuttle can move electrons between quantum dots separated by a few micrometres in about a nanosecond. Moreover, Bäuerle, Meunier and co-workers have shown that loading an electron onto the shuttle and unloading it again also only takes about a nanosecond. This suggests that an electron could be transferred from one quantum dot to another well before it loses its spin coherence. Indeed, in an earlier experiment4 it was shown that electrons in a similar shuttle kept their spin coherence for approximately 25 ns. However, these electrons were not picked up from and delivered to quantum dots. The next challenge, therefore, is to measure if spin coherence can indeed be maintained during transfer between quantum dots, which is essential for applications in quantum computing. The new single-electron shuttle has two main ingredients: the piezoelectric effect and surface acoustic waves. When a piezoelectric material such as gallium arsenide (GaAs) is strained, electric charge accumulates and an electric potential is created. Both groups use surface acoustic waves (sound waves concentrated at the surface of a solid) to strain GaAs nanowires. This produces an oscillating electric potential that travels along the nanowire with the acoustic wave, with the minima of this potential dragging single electrons along the nanowire (Fig. 1). If the single-electron shuttle does preserve spin coherence, it will open the door to a host of exciting applications. Ways of manipulating and using quantum information that have so far been the domain of quantum optics may soon become feasible with electrons in solids. For instance, it may become possible to test Bell inequalities with electrons or to teleport the quantum state of an electron. The electronic versions of such experiments will have certain advantages over their quantum optics counterparts; for example, unlike photons, electrons in solids naturally interact and readily exchange information with each other. Most notably a coherent single-electron shuttle will open an array of new possibilities for the design of an electronic quantum computer. ❐