does an external magnetic field destroy quantum coherence

Two RF voltages are used, one for each Ti spin resulting in a novel double-resonance spectroscopy. Titanium spin 1 is driven by the magnetic STM tip while Ti spin 2 is driven by its neighboring iron atom. We believe that computational protocols that rely on the coherent control of multiple spins on a surface are now within reach. This breakthrough enables the coherent control of multiple spins coupled to each other using one STM tip. The remote spin (Ti-2) is driven by the combination of the resonant electric field from the tip and its interaction with the neighboring iron spin, which acts like a permanent single-atom magnet. Here, we used one Ti spin in the tunnel junction as an ESR sensor to measure the spin states of a second Ti spin, called the remote spin, which was weakly coupled to the first. This breakthrough work gives a glimpse at the potential power of controlling multiple qubits on a surface in an atomically engineered nanostructure. In 2021, QNS researchers used their “Alice” and “Bob” tools to extend ESR STM from the control of single spins to multiple spins. QNS has been a leader in ESR STM from the very beginning. According to the basic ESR equation, a higher field requires a higher frequency. Here the x-axis is the frequency of the RF voltage and the y-axis is the tunnel current. For the experts, the minimum linewidth of ESR-STM is on order of MHz which corresponds to about 10 neV. The exquisite energy resolution of ESR STM can be appreciated here by pointing out that magnetic fields of 0.65 T and 0.70 T result in well-separated ESR spectra. One can also clearly see that the Zeeman energy, and hence the frequency of the ESR resonance, changes in proportion to the magnitude of magnetic field. We see the ESR signals as current changes of several hundreds of femto-ampere (10-12 A), when the RF voltage is resonant with the Zeeman energy. With this set of ingredients, we are able to electrically drive the spin resonance of atoms and molecules on a surface.Ī typical ESR-STM spectrum is obtained by measuring the change of the tunnel current while sweeping the frequency of the RF voltage at a fixed external magnetic field, see Figure 2. And fourth, a high-frequency oscillating electric field is applied between tip and sample. Third, an external magnetic field is used to adjust the Zeeman energy of the quantum spin on the surface to be in resonance with the RF electric field. Second, the tip needs to be spin-polarized in order to measure the states of the spin on the surface. First, the spin needs to be decoupled from a metallic substrate via a thin insulating film in order to maintain its quantum-ness. We add a GHz frequency RF voltage to the normal DC tunnel voltage that is applied between tip and sample.įigure.2 ESR spectra of Ti spin on MgO There are several key ingredients highlighted in Figure 2. The STM tip contains a magnetic apex (grey arrow) which results in a spin-polarized tunnel current. A quantum spin (yellow) is put on a thin insulating film (purple) that is supported on a metal substrate (grey). This led to the key idea, conceived in 2008 by QNS’s director and his colleague, Arzhang Ardavan from Oxford University, to realize that RF frequency oscillating electric fields in the tunnel junction could be used to drive ESR in an STM, illustrated in Figure 1. On the other hand, an STM tunnel junction always contains strong electric fields. However, incorporating such an approach into an STM is very difficult and has not been achieved to date. This is usually achieved by using a special cavity to enhance those fields. Ensemble ESR uses oscillating magnetic fields at RF frequencies (10 - 100 GHz) to drive and sense the spin resonance. This integration of two techniques allows us to achieve the single spin sensitivity at atomic precision. Figure.1 ESR.STM The combination of ESR with STM merges some of the most powerful advantages of both techniques: The atomic-scale spatial resolution of STM with the much higher energy resolution of ESR.

Does an external magnetic field destroy quantum coherence