Ultrafast Fourier Transform with a Femtosecond-Laser-Driven Molecule

Wave functions of electrically neutral systems can be used as information carriers to replace real charges in the present Si-based circuit, whose further integration will result in a possible disaster where current leakage is unavoidable with insulators thinned to atomic levels. We have experimentally demonstrated a new logic gate based on the temporal evolution of a wave function. An optically tailored vibrational wave packet in the iodine molecule implements four- and eight-element discrete Fourier transform with arbitrary real and imaginary inputs. The evolution time is 145 fs, which is shorter than the typical clock period of the current fastest Si-based computers by 3 orders of magnitudes.

Figure 1

Schematic of the present DFT with an example: $\frac{1}{2}(1,-i,-1,i)\to (0,1,0,0)$. The common transform matrices ${\mathbf{w}}_4$ and ${\mathbf{w}}_4^{-1}$ are operated for any arbitrary inputs and outputs, respectively, by the indicated hardware.

Figure 2

Input and output of the UFFT. (i) Population spectra; (ii) and (iii) interferograms of the input and reference WPs at $t=0\mathrm{fs}$ and $\sim 145\mathrm{fs}$. (a), (h), and (A) represent the results obtained with the inputs (a), (h), and (A) listed in Table  and the supplementary material [23]. The same color denotes the same vibrational level among (i), (ii), and (iii). The origin of the relative phase ($\theta =0$) is arbitrary, and it denotes the position of the peak of the interferograms of $v=38$ for (a) and (h), and $v=32$ for (A). Dots are measured data, and solid lines are the sine functions least-square fitted to the measured interferograms with their periods fixed to $2\pi$. The measurement of each interferogram and its least-square fitting have been carried out for a broader range of $\theta$ [25].