Spin-valley locked excited states spectroscopy in a one-particle bilayer graphene quantum dot

Abstract

Current semiconductor qubits rely either on the spin or on the charge degree of freedom to encode quantum information. By contrast, in bilayer graphene the valley degree of freedom, stemming from the crystal lattice symmetry, is a robust quantum number that can therefore be harnessed for this purpose. The simplest implementation of a valley qubit would rely on two states with opposite valleys as in the case of a single-carrier bilayer graphene quantum dot immersed in a small perpendicular magnetic field ($B_{\perp }\lesssim 100$mT). However, the single-carrier quantum dot excited states spectrum has not been resolved to date in the relevant magnetic field range. Here, we fill this gap, by measuring the parallel and perpendicular magnetic field dependence of this spectrum with an unprecedented resolution of $4\mu$eV. We use a time-resolved charge detection technique that gives us access to individual tunnel events. Our results come as a direct verification of the predicted spectrum and establish a new upper-bound on inter-valley mixing, equal to our energy resolution. Our charge detection technique opens the door to measuring the relaxation time of a valley qubit in a single-carrier bilayer graphene quantum dot.

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Cited by in corpus (9)

• Spin-Valley Protected Kramers Pair in Bilayer Graphene
• Electric-field independent spin-orbit coupling gap in hBN-encapsulated bilayer graphene
• Electrically-tunable graphene nanomechanical resonators
• Tunable spin-orbit splitting in bilayer graphene/WSe${}_2$ quantum devices
• Entropy spectroscopy of a bilayer graphene quantum dot
• Electric field tunable spin-orbit gap in a bilayer graphene/WSe${}_2$ quantum dot
• Transport approach to quantum state tomography
• Coherent and Dissipative Spin Torques in Quantum Dots: A Unified Framework for Quantum Spin Dynamics
• Electric spin and valley Hall effects