IQST Young Researcher Project

Detecting single spins in biological molecules

Project Description:

Single color centers in diamond and especially the nitrogen-vacancy centers (NV) have remarkable physical properties with a wide range of applications, e.g. qubits, single photon sources and nano-scale ultra sensitive magnetic field sensors. We have recently demonstrated that by measuring a shallow (2 nm deep) NV we can detect nuclear spins on the diamond surface with single spin sensitivity (C. Müller at al., Nature Communications 5:4703 (2014)). In these experiments the magnetic dipolar coupling to the nuclear spins is much stronger compared to the coupling among the spins on the surface. In this case we cannot consider the system as sensor and sample separately, but we have to describe it using a Hamiltonian including all the spins. We want to further explore this “quantum” regime by studying single spin labeled biological molecules using shallow NV centers. In our project we plan to implement the recently proposed methods for “quantum enhanced sensing”. The basic idea is to create a correlated quantum state, e.g. entanglement, between two or more spins and use this new state as a sensor. The advantage over the single spin approach is better sensitivity and bandwidth, compared to uncorrelated quantum states. In our realization in the experiment we plan to use three approaches. In the first one we will implement the quantum error correction protocol for sensing of single spins (G. Arrad et al., Phys. Rev. Lett. 112, 150801 (2014); E. M. Kessler, et al., Phys. Rev. Lett. 112, 150802 (2014)) by using a single NV and a neighboring 13C nuclear spin. The second experiment will be to create an entanglement between two strongly coupled NVs and use it to detect external spins. The novelty here is not only the improved sensitivity for the same acquisition time, but also that certain entangled states are not sensitive to magnetic fields, but to field gradients. In the last experiment we plant to couple a single shallow NV to a single external auxiliary electron spin, which is couple to further away spins (nuclear or electron) we want to measure. The main challenge is the fabciration of stable shallow NVs centers, where we have demonstrated the first successful steps, see the figure below.

Further Collaborations:

  • Prof. Dr. Fedor Jelezko (Ulm)
  • Prof. Dr. Martin Plenio (Ulm)

Selected Recent Publications:

Increasing the creation yield of shallow single defects in diamond by surface plasma treatment, C. Osterkamp et al., Appl. Phys. Rev. Lett. 103, 193118 (2013)

Stabilizing shallow color centers in diamond created by nitrogen delta-doping using SF6 plasma treatment, C. Osterkamp et al.,Appl. Phys. Lett. 106, 113109 (2015).