Cryogenic Memory Array based on Ferroelectric SQUID and Heater Cryotron
Shamiul Alam, Md Mazharul Islam, Md Shafayat Hossain, Kai Ni, Vijaykrishnan Narayanan, Ahmedullah Aziz
Abstract
Cryogenic (cryo) memory devices, designed to operate at/below 4 Kelvin (K) temperature, is a prime enabler of practical quantum computing systems, and superconducting (SC) electronic platforms (Figs. 1(a), (b)) [1]. The state-of-the-art quantum algorithms require many arbitrary rotations which demand a large memory to store program instructions [2]. SC qubits (used in most of the existing quantum computing systems) are highly sensitive to noise and hence, to protect the qubit states from thermal disturbances, they are placed at a few milli-Kelvin (mK) temperature. Furthermore, to preserve the integrity of the quantum states, the SC qubits undergo continuous error correction schemes, requiring extensive memory and bandwidth [2]. Superconducting electronics (SCE) (targeted towards space applications, and high-performance computing) outperforms the conventional CMOS counterparts in terms of speed and energy-efficiency (Fig. 1(c)) [3]. Decades of research efforts have given rise to three major categories (and several sub-variants) of cryo-memories based on SC, non-SC, and hybrid technologies (Fig. 2) [2], [4]–[6]. However, the existing variants suffer from one or more of the following challenges - (i) limited scalability, (ii) process complexity, (iii) bulky peripherals, (iv) array-level interference, (v) volatility, and (vi) speed incompatibility. Therefore, a scalable cryo-memory system remains elusive. To address these existing issues, here, we present a novel cryo-memory system utilizing -(i) the polarization-induced Cooper-pair [7] modulation in a ferroelectric <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(FE)$</tex> superconducting quantum interference device (SQUID) (Fig. 3(a)) [8], and (ii) current controlled <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$SC\leftrightarrow non-SC$</tex> switching in a heater cryotron <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(hTron)$</tex> (Fig. 4) [4]. Discrete prototypes of these devices have been demonstrated recently, but their coupled interactions (which we harness in our work) were never explored before.