Adds functions for calculating the total photon distribution of k lossy squeezed states #230
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thisac
approved these changes
Mar 15, 2021
thewalrus/quantum/fock_tensors.py
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| @@ -608,7 +608,7 @@ def tvd_cutoff_bounds(mu, cov, cutoff, hbar=2, check_is_valid_cov=True, rtol=1e- | |||
| and the user provided cutoff. | |||
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| For the derivation see Appendix B of `'Exact simulation of Gaussian boson sampling in polynomial space and exponential time', | |||
| Quesada and Arrazola et al. <10.1103/PhysRevResearch.2.023005>`_. | |||
| Quesada and Arrazola <10.1103/PhysRevResearch.2.023005>`_. | |||
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Wouldn't the full URL be needed here for the link to work? Although this function doesn't seem to be rendered in the docs at all. 🤔
Suggested change
| Quesada and Arrazola <10.1103/PhysRevResearch.2.023005>`_. | |
| Quesada and Arrazola <https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.2.023005>`_. |
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| def total_photon_number_distribution(n, k, s, eta, pref=1.0): | ||
| r"""Probability of observing a total of :math:`n` photons when :math:`k` identical | ||
| single-mode squeezed vacua with squeezing parameter s undergo loss by transmission :math:`\eta`. |
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I've actually never seen the word "vacua" before. 😄
Suggested change
| single-mode squeezed vacua with squeezing parameter s undergo loss by transmission :math:`\eta`. | |
| single-mode squeezed vacua with squeezing parameter ``s`` undergo loss by transmission :math:`\eta`. |
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Or actually change this to use :math:s as below. Same below for my n to :math:n suggestion.
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thewalrus/tests/test_quantum.py
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| """Test that the total photon number distribution has the correct mean and variance""" | ||
| expectation_n = characteristic_function(s = s, k = k, eta = eta, poly_corr=1, mu = 0) | ||
| expectation_n2 = characteristic_function(s = s, k = k, eta = eta, poly_corr=2, mu = 0) | ||
| var_n =expectation_n2 - expectation_n ** 2 |
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Suggested change
| var_n =expectation_n2 - expectation_n ** 2 | |
| var_n = expectation_n2 - expectation_n ** 2 | |
thewalrus/tests/test_quantum.py
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| expectation_n = characteristic_function(s = s, k = k, eta = eta, poly_corr=1, mu = 0) | ||
| expectation_n2 = characteristic_function(s = s, k = k, eta = eta, poly_corr=2, mu = 0) |
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Suggested change
| expectation_n = characteristic_function(s = s, k = k, eta = eta, poly_corr=1, mu = 0) | |
| expectation_n2 = characteristic_function(s = s, k = k, eta = eta, poly_corr=2, mu = 0) | |
| expectation_n = characteristic_function(s=s, k=k, eta=eta, poly_corr=1, mu=0) | |
| expectation_n2 = characteristic_function(s=s, k=k, eta=eta, poly_corr=2, mu=0) |
thewalrus/tests/test_quantum.py
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| @pytest.mark.parametrize("k", [4, 6, 10, 12]) | ||
| @pytest.mark.parametrize("eta", [0, 0.1, 0.5, 1]) | ||
| def test_characteristic_function_is_normalized(s, k, eta): | ||
| r"""Check that when evaluated at \mu=1 the characteristic function gives 1""" |
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Suggested change
| r"""Check that when evaluated at \mu=1 the characteristic function gives 1""" | |
| r"""Check that when evaluated at mu=1 the characteristic function gives 1""" | |
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It seems to me like this function evaluates at mu=0 rather than mu=1 as is stated here. Typo? 🤔
thewalrus/tests/test_quantum.py
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| # Note that s must be less than np.arctanh(np.sqrt(0.5)) ~= 0.88 | ||
| p = np.tanh(s)**2 | ||
| val = characteristic_function(k=k, s=s, eta=1.0, mu=mu) | ||
| expected = ((1-p)/(1-2*p))**(k/2) |
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Suggested change
| expected = ((1-p)/(1-2*p))**(k/2) | |
| expected = ((1 - p) / (1 - 2 * p)) ** (k / 2) | |
thewalrus/tests/test_quantum.py
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| @pytest.mark.parametrize("k", [4, 6, 10, 12]) | ||
| def test_charactetistic_function_no_loss(s, k): | ||
| """Check the values of the characteristic function when there is no loss""" | ||
| mu = mu = 0.5*np.log(2) |
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Suggested change
| mu = mu = 0.5*np.log(2) | |
| mu = 0.5 * np.log(2) | |
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yeah, not sure about the complex code in |
Co-authored-by: Theodor <theodor@xanadu.ai>
Co-authored-by: Theodor <theodor@xanadu.ai>
nquesada
commented
Mar 15, 2021
Codecov Report
@@ Coverage Diff @@
## master #230 +/- ##
=========================================
Coverage 100.00% 100.00%
=========================================
Files 21 21
Lines 1200 1228 +28
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+ Hits 1200 1228 +28
Continue to review full report at Codecov.
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This PR implements the results in Appendix 5 and Eqs. 8 and 9 of https://arxiv.org/pdf/2102.12474.pdf