“…Reinforcement learning, a subfield of machine learning, has had outstanding success in tasks ranging from board games [10] to robotics [11]. Reinforcement learning, however, has only very recently been started to be applied to complex physical systems, with training performed either on simulations [12][13][14][15][16][17][18] or directly in experiments [19][20][21][22][23][24][25][26], for example in laser [19,22,26], particle [20,21], softmatter [23] and quantum physics [24,25]. Specifically in the quantum domain, during the past few years, a number of theoretical works have pointed out the great promises of reinforcement learning for tasks covering state preparation [27][28][29][30][31], gate design [32], error correction [33][34][35] and circuit optimization/compilation [36,37], making it an important part of the machine learning toolbox for quantum technologies [38][39][40].…”