Boson sampling for molecular vibronic spectra

Journal name:
Nature Photonics
Year published:
Published online


Controllable quantum devices open novel directions to both quantum computation and quantum simulation. Recently, a problem known as boson sampling has been shown to provide a pathway for solving a computationally intractable problem without the need for a full quantum computer, instead using a linear optics quantum set-up. In this work, we propose a modification of boson sampling for the purpose of quantum simulation. In particular, we show that, by means of squeezed states of light coupled to a boson sampling optical network, one can generate molecular vibronic spectra, a problem for which no efficient classical algorithm is currently known. We provide a general framework for carrying out these simulations via unitary quantum optical transformations and supply specific molecular examples for future experimental realization.

At a glance


  1. Pictorial description of boson sampling and molecular vibronic spectroscopy.
    Figure 1: Pictorial description of boson sampling and molecular vibronic spectroscopy.

    a, Boson sampling consists of sampling the output distribution of photons obtained from quantum interference inside a linear quantum optical network. b, Vibronic spectroscopy uses coherent light to excite electronically an ensemble of identical molecules and measures the re-emitted (or scattered) radiation to infer the vibrational spectrum of the molecule. We show in this work how the fundamental physical process that underlies b is formally equivalent to situation a, together with a step to prepare a nonlinear step.

  2. Boson sampling apparatus for vibronic spectra.
    Figure 2: Boson sampling apparatus for vibronic spectra.

    a, The boson sampling apparatus modified according to a direct implementation of equation (9). b, The boson sampling apparatus modified according to equation (11). Here the difference with the usual set-ups for the typical boson sampling problem is confined to the preparation process of the input state. For simplification, . Green and red boxes after the first unitary operations represent the prepared initial states, which are identified as squeezed vacuum and squeezed coherent states, respectively. The wavy yellow lines that enter the interferometer represent the preoperative initial states, which are vacuum states in this figure. They could be non-vacuum states for the proposed extension of the theory.

  3. FCP (black sticks) of formic acid
    Figure 3: FCP (black sticks) of formic acid

    (11A′  12A′) for a symmetry block . The red curve is taken from the experimental spectrum in Leach et al.40

  4. FCP (black sticks) of thymine
    Figure 4: FCP (black sticks) of thymine

    (11A′  12A″). The red curve, whose FCP is shifted to be compared clearly, is taken from the experimental spectrum in Choi et al.29


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  1. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA

    • Joonsuk Huh,
    • Gian Giacomo Guerreschi,
    • Borja Peropadre,
    • Jarrod R. McClean &
    • Alán Aspuru-Guzik


J.H., G.G.G. and A.A.-G. conceived and designed the experiments. J.H. and G.G.G. performed the simulations. J.H., G.G.G., B.P. and J.R.M. contributed materials and/or analysis tools. J.H., G.G.G., B.P., J.R.M. and A.A.-G. worked on the theory, analysed the data and wrote the paper.

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