Aleph - 0.31.1

🚀 Highlights

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✨ New Features

• Introduced the Plotting module to create figures in Aleph for data analysis, including bar, line, scatter, and heatmap plots.
  • Supports legends, multiple series, multiple plots in the same figure, and a ton of customization options.
• Functions for the computation of matrix elements and expectation values with MPS and MPO.
  • matrix_element(bra,operator,ket) to compute the matrix element $\bra{\phi} O \ket{\psi}$ of an operator.
  • expval(operator,ket) to compute the expected value $\bra{\psi} O\ket{\psi}$ of the operator.
• Added accumulators for binning analysis of time series and markov chain data. Currently support accumulator("no_binning") and accumulator("binning"). The bin size can be set via accumulator("binning" ["bin_size" : 1024 ]).
• Added a FourBody symbolic fermionic operator: $c^{\dag}_{i}c^{\dag}_j c_k c_l$. An operator can be created via FourBody(i,j,k,l) where i,j,k,l are the sites where the operator acts.
• Added a DoubleExcitation fermionic operator: $c^{\dag}_{i}c^{\dag}_j c_k c_l + h.c.$. An operator can be created via DoubleExcitation(i,j,k,l) where i,j,k,l are the sites where the operator acts.
• The array and matrix factories now accept array and matrix objects together with a type tag. For example: array(my_matrix, as_complex) will create a complex array from my_matrix even if it is of real type.
• MPS compression routine. mps.compress(tol) to compress a MPS to specified error tolerance.
• operator_function now supports both Hermitian and non-Hermitian matrices and operators. The appropriate Krylov method (Lanczos or Arnoldi) is automatically selected based on the input. The API can be summarized as:
  • operator_function(H, dim, fun(real){real}, ["is_real":true]) for real-valued functions and Hermitian operators. Note that the ["is_real":true] option is required to indicate that the function is real-valued.
  • operator_function(H, dim, fun(complex){complex}) for other Hermitian operators.
  • operator_function(H, dim, fun(complex, integer){complex}) for non-Hermitian operators. The integer argument stands for the order of the derivative of the function, which is required for non-Hermitian operators.
  • Any of the above can also be called with a matrix Hmat instead of an operator H and a dimension dim.
  • Any of the above also accepts an optional dictionary of options as last argument, e.g. ["krylov_dimension": 32].
• The PhaseHop(angle,i,j) factory function has been added to create fermionic hopping operators with an associated phase factor: $e^{i \cdot angle} c^{\dag}_i c_j + \mathrm{h.c.}$.

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🐛 Fixes

• Assigning complex arrays or matrices to real arrays or matrices used to silently fail, it now raises an error.

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⚙️ Internal / Technical Changes

• Adds internal support for handling sparse matrix operations with free fermion objects.

• Real arrays and matrices are not implicitly convertible to complex arrays and matrices anymore. An explicit conversion is now required using as_complex.

• Cmake presets to help manage compilation with IDE/VScode.

  • Presets for qbitpp
  • Presets for chaiqpp

• VScode devcontainer mount the user's .ssh for syncing with gitlab.

  • no further setup required for syncing git, if the user already has set his ssh keys in $HOME/.ssh

⚠️ Breaking Changes

• operator_function API has changed to support both Hermitian and non-Hermitian operators; it now accepts an option map similar to that of iterative_eigensolver. See the New Features section for details.

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🧪 Migration Notes

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