No abstract

The electrical properties of ferroelectric substances are investigated and related to the Curie-Weiss law. A cryogenic experiment suitable for students measures the electrical susceptibility of strontium titanate in the 90-300 K temperature range. By measuring the electrical susceptibility of a modified barium titanate ceramic between 273 K and 343 K a phase transition is clearly observed at 304 K.

A scaled-up quantum computer will require a highly efficient control interface that autonomously manipulates and reads out large numbers of qubits, which for solid-state implementations are usually held at millikelvin (mK) temperatures. Advanced CMOS technology, tightly integrated with the quantum system, would be ideal for implementing such a control interface but is generally discounted on the basis of its power dissipation that leads to heating of the fragile qubits. Here, we demonstrate an ultra low power, CMOS-based quantum control platform that takes digital commands as input and generates many parallel qubit control signals. Realized using ∼ 100,000 transistors operating near 100 mK, our platform removes the need for separate control lines to every qubit by exploiting the low leakage of transistors at cryogenic temperatures to store charge on floating gate structures that are used to tune-up quantum devices. This charge can then be rapidly shuffled between on-chip capacitors to generate the fast voltage pulses required for dynamic qubit control. We benchmark this architecture on a quantum dot test device, showing that the control of thousands of gate electrodes is feasible within the cooling power of commercially available dilution refrigerators.

A cryogenic experiment determining the dielectric susceptibility of the ferroelectric substance, strontium titanate, in the 90-to 300-K temperature range is described. Evidence is presented for a structural phase transition in strontium titanate at 110 K. The experiment is suitable for advanced students.