1. Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California, USA
2. Department of Chemistry, Stanford University, Stanford, California, USA;
3. Current affiliation: Italian Institute of Technology, Genova, Italy
4. Department of Management Science and Engineering, Stanford University, Stanford, California, USA
5. Current affiliation: Sandia National Laboratories, Livermore, California, USA
6. Italian Institute of Technology, Genova, Italy