Release 0.16.0

New features since last release

• Adds the ability to construct time domain multiplexing algorithms via the new sf.TDMProgram class, for highly scalable simulation of Gaussian states. (#440)

  For example, creating and simulating a time domain program with 2 concurrent modes:

  >>> import strawberryfields as sf
  >>> from strawberryfields import ops
  >>> prog = sf.TDMProgram(N=2)
  >>> with prog.context([1, 2], [3, 4], copies=3) as (p, q):
  ...     ops.Sgate(0.7, 0) | q[1]
  ...     ops.BSgate(p[0]) | (q[0], q[1])
  ...     ops.MeasureHomodyne(p[1]) | q[0]
  >>> eng = sf.Engine("gaussian")
  >>> results = eng.run(prog)
  >>> print(results.all_samples)
  {0: [array([1.26208025]), array([1.53910032]), array([-1.29648336]),
  array([0.75743215]), array([-0.17850101]), array([-1.44751996])]}

  For more details, see the code documentation.

• Adds the function VibronicTransition to the apps.qchem.vibronic module. This function generates a custom Strawberry Fields operation for applying the Doktorov operator on a given state. (#451)

  >>> from strawberryfields.apps.qchem.vibronic import VibronicTransition
  >>> modes = 2
  >>> p = sf.Program(modes)
  >>> with p.context as q:
  ...     VibronicTransition(U1, r, U2, alpha) | q

• Adds the TimeEvolution function to the apps.qchem.dynamics module. This function generates a custom Strawberry Fields operation for applying a time evolution operator on a given state. (#455)

  >>> modes = 2
  >>> p = sf.Program(modes)
  >>> with p.context as q:
  ...     sf.ops.Fock(1) | q[0]
  ...     sf.ops.Interferometer(Ul.T) | q
  ...     TimeEvolution(w, t) | q
  ...     sf.ops.Interferometer(Ul) | q

  where w is the normal mode frequencies, and t the time in femtoseconds.

• Molecular data and pre-generated samples for water and pyrrole have been added to the data module of the Applications layer of Strawberry Fields. For more details, please see the data module documentation (#463)

• Adds the function read_gamess to the qchem module to extract the atomic coordinates, atomic masses, vibrational frequencies, and normal modes of a molecule from the output file of a vibrational frequency calculation performed with the GAMESS quantum chemistry package. (#460)

  >>> r, m, w, l = read_gamess('../BH_data.out')
  >>> r # atomic coordinates
  array([[0.0000000, 0.0000000, 0.0000000],
         [1.2536039, 0.0000000, 0.0000000]])
  >>> m # atomic masses
  array([11.00931,  1.00782])
  >>> w # vibrational frequencies
  array([19.74, 19.73, 0.00, 0.00, 0.00, 2320.32])
  >>> l # normal modes
  array([[-0.0000000e+00, -7.5322000e-04, -8.7276210e-02,  0.0000000e+00,
       8.2280900e-03,  9.5339055e-01],
     [-0.0000000e+00, -8.7276210e-02,  7.5322000e-04,  0.0000000e+00,
       9.5339055e-01, -8.2280900e-03],
     [ 2.8846925e-01, -2.0000000e-08,  2.0000000e-08,  2.8846925e-01,
      -2.0000000e-08,  2.0000000e-08],
     [ 2.0000000e-08,  2.8846925e-01, -2.0000000e-08,  2.0000000e-08,
       2.8846925e-01, -2.0000000e-08],
     [-2.0000000e-08,  2.0000000e-08,  2.8846925e-01, -2.0000000e-08,
       2.0000000e-08,  2.8846925e-01],
     [-8.7279460e-02,  0.0000000e+00,  0.0000000e+00,  9.5342606e-01,
      -0.0000000e+00, -0.0000000e+00]])

Improvements

• When jobs submitted to the Xanadu Quantum Cloud are canceled, they will now display a cancel_pending JobStatus until the cancellation is confirmed. (#456)

Bug fixes

• Fixed a bug where the function reduced_dm in backends/tfbackend/states.py gives the wrong output when passing it several modes. (#471)

• Fixed a bug in the function reduced_density_matrix in backends/tfbackend/ops.py which caused the wrong subsystems to be traced out. (#467) (#470)

• Fixed a bug where decompositions to Mach-Zehnder interferometers would return incorrect results on NumPy 1.19. (#473)

• The Walrus version 0.14 introduced modified function names. Affected functions have been updated in Strawberry Fields to avoid deprecation warnings. (#472)

Documentation

• Adds further testing and coverage descriptions to the developer documentation. This includes details regarding the Strawberry Fields test structure and test decorators. (#461)

• Updates the minimum required version of TensorFlow in the development guide. (#468)

Contributors

This release contains contributions from (in alphabetical order):

Juan Miguel Arrazola, Tom Bromley, Theodor Isacsson, Josh Izaac, Soran Jahangiri, Nathan Killoran, Fabian Laudenbach, Nicolás Quesada, Antal Száva, ‪Ilan Tzitrin.