Quantum Dot Chains for Low-Heating Majorana Coupling Control
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Solution Overview
Problem
Conventional methods for controlling tunable couplings between Majorana zero modes (MZMs) using cutter gates require large voltage pulses, leading to increased qubit error probability due to heating, which is exponentially suppressed by the topological gap and charging energy.
Innovation Solution
Utilize chains of quantum dots with plunger gates to control tunable couplings between MZMs, allowing for smaller voltage swings and reducing the need for compensating pulses on nearby gates, thereby minimizing qubit heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cutter gates are used to control coupling between MZMs, then coupling control is achieved, but large voltage pulses are required leading to increased qubit heating and error probability
Solution Approach 1:
The patent introduces an intermediary quantum dot system between the MZMs and the voltage control mechanism. Instead of applying large voltage pulses directly to cutter gates, the invention uses a sequence of smaller voltage pulses to control quantum dot occupancy, which in turn mediates the coupling between MZMs. This intermediary approach allows indirect control of the coupling strength without directly heating the MZM system through large voltage swings.
Solution Approach 2:
The invention changes the control parameter from direct voltage amplitude control of cutter gates to quantum dot occupancy control through sequential pulse application. By changing which parameters are controlled (dot occupancy rather than direct coupling voltage), the system achieves coupling control with smaller voltage excursions, reducing thermal effects and error rates.
2Ease of operation
If large amplitude voltage pulses are applied to cutter gates, then coupling control is achieved, but control complexity increases and qubit heating occurs
Solution Approach 1:
The patent segments the single large voltage pulse control into multiple smaller sequential pulses applied to different quantum dots. Instead of one complex high-amplitude pulse to a cutter gate, the invention divides the control into a sequence of simpler, lower-amplitude pulses to individual quantum dots, making each control operation easier while achieving the same coupling effect through the cumulative effect on MZM interaction.
Solution Approach 2:
The quantum dots serve as intermediary control elements that simplify the operation. Rather than directly controlling MZM coupling with complex large-amplitude pulses, the system uses quantum dots as mediators that respond to simpler control signals, reducing the complexity of the control waveform requirements while maintaining effective coupling control.
Data Source
AI summary
Quantum devices with chains of quantum dots for controlling tunable couplings between Majorana zero modes (MZMs) are described. Methods for controlling tunable couplings between MZMs using such chains of quantum dots are also described. An example quantum device comprises at least one superconducting island configurable to support at least one pair of Majorana zero modes (MZMs). The quantum device may further include a region adjacent to at least one MZM of the at least one pair of MZMs, where the region is configurable to realize a chain of quantum dots for controlling a tunable coupling between the at least one MZM of the at least one pair of MZMs and another MZM.