Broadband Population Transfer Based on Suture Adiabatic Pulses

Abstract

High-fidelity coherent population transfer plays a vital role in the realization of quantum memories. However, population transfer with high performance across a broad frequency range is still challenging due to the finite Rabi coupling strength limited by laser powers. Here we propose a novel population-transfer scheme by suturing adiabatic control pulses with each pulse covering certain frequency interval, which are connected in a way that neighboring adiabatic pulses have opposite chirping directions. Taking the widely utilized hyperbolic-square-hyperbolic pulse as an example, we demonstrate that rapid and robust population transfer can be achieved. The transfer bandwidth scales linearly with the number of suture pulses while maintaining high fidelity, even at the suture points where adiabaticity breaks down. Crucially, these pulses can be realized by a single laser by means of temporal multiplexing. For a given bandwidth, this strategy substantially reduces the operational time which is necessary for on demand read-out and suppressing decoherence effects. Our scheme enables a dramatic increase in multimode storage capacity and paves the way for realizing practical quantum networks.

Figures (9)

• Figure 1: (a) Schematic diagram of AFC-SW protocol: An inhomogeneously broadened transition $\ket{g} \to \ket{e}$ is engineered into frequency combs (periodicity $\Delta_{0}$, bandwidth $W$). Signal pulse $\Omega_s$ excites comb modes, then a pair of control pulses $\Omega_c$ working on $\ket{e} \leftrightarrow \ket{s}$ implement write and read process to emit the signal after certain storage time; (b) AFC-SW protocol illustrated by time-order: Time sequence of an AFC echo memory could be retrieved with certain time interval $t_{s}$ by applying a pair of control pulses; (c) Set up of SAP3 : we utilize single laser three times by reflect it twice, using proper AOMs to create three different frequency component of control beams working on the memory and and this scheme could be extended to SAPn.
• Figure 2: Pulse shape of SAP1 (a) and SAP2 (d), with $\Delta_{1}(t)=\Delta(t)+\frac{f}{2}, \Delta_{2}(t)=-\Delta(t)-\frac{f}{2}$. Two dimensional population transfer fidelity plots that illustrate bandwidth scaling relation with pulse duration $\tau$ and Rabi frequency $\Omega$ of SAP1 (b) (c) and SAP2 (e) (f). We set $\Omega =$ 4 MHz, $t_{1}$ = 1 $\mu s$, $r = 2$ MHz, $r_{1} = 2$ MHz, $T = 0.5$$\mu s$ for (a) and (d); $\Omega =$ 2 MHz, $t_{1}$ = 1 $\mu s$, $r=1.2~$MHz, $r_{1}=0.7~$MHz, $T=0.35~\mu s$ for (b) and (e); $\tau = 6$$\mu$s, $t_{1}$ = 1 $\mu s$, $r=0.3\times\Omega^{2}, r_{1}=0.15\times\Omega^{2}, T = 0.4~\mu s$ for (c) and (f).
• Figure 3: Comparison of population transfer fidelity $F$ for three control pulses across four key parameters with fixed $t_{1}$ = 0.5 $\mu s$ while other parameters ($T,r,r_{1}$) optimized for (a)(b)(c) and ($r,r_{1}$) optimized for (d). (a) $F$ as a function of maximum Rabi frequency $\Omega$ (fixed $\tau$ = 5 $\mu s$, $W$ = 100 MHz); (b) $F$ as a function of pulse duration $\tau$ (fixed $\Omega =$ 4 MHz, $W$ = 100 MHz); (c) $F$ as a function of bandwidth $W$ (fixed $\Omega =$ 4 MHz, $\tau$ = 5 $\mu s$); (d) $F$ as a function of pulse shape parameter $T$ ( fixed $\Omega =$ 4 MHz, $\tau$ = 6 $\mu s$, $W$ = 100 MHz).
• Figure 4: Contour plots of population transfer fidelity $F$ as a function of maximum Rabi frequency $\Omega$ and the pulse duration $\tau$ over bandwidth of 50 MHz in (a) (b) and 80 MHz in (c) (d), with control protocols SAP1 in (a) (c) and SAP3 in (b) (d). The parameters ($T, r, r_{1}$) are optimized with fixed $t_{1}$ = 0.5 $\mu$s.
• Figure 5: (a) Phase diagram depicting population transfer fidelity $F$ near 0.95 across three distinct pulses as a function of bandwidth $W$ and pulse duration $\tau$ with fixed maximum Rabi frequency $\Omega$= 3 MHz and $t_{1}$ = 0.5$\mu s$; (b) Phase diagram depicting population transfer fidelity $F$ near 0.95 across three distinct pulses as a function of bandwidth $W$ and maximum Rabi frequency $\Omega$ with fixed pulse duration $\tau$= 5 $\mu$s and $t_{1}$ = 0.5$\mu s$. Other parameters ($T, r, r_{1}$) have been optimized.