China develops chip that allows for two-dimensional Quantum walks, have exponential superiority in quantum searching and quantum simulation applications

Quantum walks are the quantum version of classical random walks, which are a mathematical means for describing a natural random walk, e.g., simply wandering around randomly.

In a “classical random walk”, you could imagine someone starting at the centre of a city, and making a random decision at each intersection. In this case, the walker’s position is described by a probability distribution over all the possible positions (kind of like the wear on a stone step is a probability distribution of where feet land).

In the quantum world, superposition (the property of quanta that they may exist in a superposition of multiple states at once until the waveform is collapsed) is added to the mix. In other words, the walker may be superposed over all positions until measured.

Chinese researchers have demonstrated a two-dimensional continuous-time quantum walk by using the external geometry of photonic waveguide arrays, rather than the inner degree of freedoms of photons. Using femtosecond laser direct writing, they constructed a large-scale three-dimensional structure that forms a two-dimensional lattice with up to 49 × 49 nodes on a photonic chip.