 Pick about calorimetry of an individual facelift, please the floor is yours so hello everybody and Thank you for giving me the opportunity to present our work Yeah, so I'm going to talk about our project which is on the Calorimetric detection of individual facelifts in a hysteretic RF squid So Calorimetry is one of the most promising methods for detecting energy quanta in mesoscopic systems and to give you Few examples for example in the quantum computing domain. There's an ongoing effort to bring the room temperature electronics to the cheap level and for basically interfacing qubits and accordingly having Detector which is capable of capturing microwave photons is an important milestone and Some measurement schemes which couples qubits to actually an Absorber can be already found in literature and Apart from that for example, we can also use the calorimetry in single tunneling electron experiments where an electron turnstile injects the electrons to the absorber at an desired energy level In our case, it's going to be the thermal signature of the tunneling of a let's say Josephson vortex In a in a hysteretic RF squid So what we have is basically a superconducting loop where the weakling is made of normal metal and So we know that if this the screening pyramid screening of this loop is weak in that case, sorry For the point can I just point this way? Yeah, okay, thank you Okay, so so if this loop has a weak screening parameter In that case, we know that the external flux that we apply and The flag that thread threads the loop is somewhat has somewhat linear relationship And now if we increase this a screening part of screening capacity of our loop in that case this relationship becomes a multivalued function, let's say and now if we Which allows us to actually Kind of cut anyways, so which allows us to sweep the external magnetic field Up to such a point that if we go further beyond we have these phase jumps and Which is an irreversible process and therefore is accompanied by instantaneous dissipation and So this dissipation maybe we can better appreciate it if you look at the energy a potential energy landscape of our device So we have a quadratic term which comes from the loop inductance and then this sinusoidal term which comes from the Josephson energy And so basically in that's a framework applying this external flux a corresponds to the to the tilting of this potential landscape To such an extent that the initial stable point is not stable anymore and that our phase particle Which represents the system states basically falls to the next valley and in that sense this difference in free energy is basically dissipated and So if you look at this circuit model of our device We see that this actually this dissipation is Absorbed by the non superconducting parts of our loop and in the form of dual heating, right? So we are we are basically a heating Actually electron electronic community of our device But as this normal part is concealed on both ends by the superconducting leads actually the the dominant relaxation mechanism is via phonon phonons and Given the fact that now actually we operate at sub Kelvin temperatures this electron phonon coupling is weakened Therefore this relaxation is actually taking it's happening in micro scale microsecond scale and So yeah, this is what we want to Resolve in real time To sum up. So yeah, we want to generate facelifts in a historic RF squid and then I resolve in real time the heat release coming from this event So in practice if you look at our squid device, so it's something like that actually we made it quite big For two reasons first, it's it's helping us to get a hysteretic It's helping us to be in the hysteretic regime and also it's helping us to get a better coupling with the flex line and Also our devices Embedded in an RLC parallel RLC circuit Such that actually which allows us to Unlike the conventional measurement schemes it allows us to do some fast measurements. We basically read the output power at the resonance with a with a high bandwidth and We also some we also have an extra piece of circuitry which allows us to impose some apply some voltage bias on our device and this way we can get the tunneling spectroscopy of our device and Also, I need to mention this third finger that is in contact with our normal metal but this time with the tunneling barrier and This way we can actually probe the density of states of the normal part and So what we see is that as this normal part is under proximity effect Means that there is already there is some pair correlations present in n and So what we get in the end here is sort of s i s prime Josephson junction And its signature we see it at actually zero bias as a zero bias conductance and So it has been shown Unfortunately, yeah, I cannot we cannot see here the references, but it has it has been shown that actually this zero bias conductance The the the temperature dependence of this zero bias conductance Can be used as a very sensitive thermometer And this is what we are showing here Basically the difference in power at between 50 millikelvin and 400 millikelvin and on the right We are basically tracing this Output power as a function of temperature what we see also is that So as proximity effect is a phase phenomenon a phase dependent phenomenon our Actually calibration curve. Let's say is also answering responding to the phase bias that we impose on the Josephson junction Okay, so Next what we show here is that these are really a small bandwidth a small a Slow magnetic field sweep measurements We are basically sweeping like applying a ramp here and then simultaneously reading the output And so what we see is that Basically, okay. Yes, something looks like this jumping first, but actually we see that Our device this kind of console confirms that we are in the hysteretic regime Because we see that the phase cannot go through full cycle of 2 pi But the jumps are taking place whenever we are reaching pi over 2 And it's not shown here, but from these measurements We can also obtain the beta the beta the screening parameter and it also confirms that actually our device is well in hysteretic regime Okay, so up to this point all of the measurements were like it is a really small bandwidth and Let's say static is steady-state measurements. So I'm kind of getting to what I promised in the beginning So next what we do is that on this flux line. We are applying a fast pulse which basically Does a back and forth and this way we get actually a two-phase slips round trip and so yeah, the the idea is to Do this in a synchronous manner with our acquisition device and observe this relaxation And so this is what we see here. This is basically the I would say the main takeaway of this Of this work so we repeated this fast measurements at different temperatures and We see that here we at the the pulse Arrives at zero microsecond and what we observe is that a violent increase of the electronic temperature the electronic community of our normal metal and then it basically Goes back to initial temperature, but it's a much slower pace due to the weakened electron-phonon coupling and as we increase the temperature Of course this first electron-phonon coupling is getting stronger. Therefore, this relaxation is now a faster But also the critical current of our Josephson junction is decreasing. Therefore, we're also depositing less power on And also the heat capacity of our absorber is getting bigger so actually we went up to 250 200 300 almost but At that at those temperatures it was just a single point and it was impossible to resolve in real-time such Relaxation so next we just concentrate on the relaxing part here and We are basically trying to show that actually This like relaxing part is in line with what theory predicts and this is the case for the Let's say the first part, but it seems as if there are two relaxation mechanisms and so Yeah, this is something we don't really understand but we argue that there's a second phonon bat maybe Due to the magnetic impurities on the surf copper surface or yeah We are open to discussion like this, but yeah It seems as though there is a secondary as slower relaxation mechanism. Yes Okay Okay, so there are a couple of reasons Do you wonder if I go back to yeah, so as you see our calibration curve our thermometer is responding to the phase as well and So to be to sit on the same calibration curve all the time We need to come back very quickly to the initial phase And if we just do a for just a step function In fact, we will be the after the jump the phase will be landing on a different point And maybe we will be basically maybe starting here and then at some point diverging to one of the other lines, okay, and The other thing is that so our it's more experimental our transmission line is Not superconducting. So if you put a step function, actually you're introducing also heat to your device Which we observe as a as a just an actually an offset in the measured power. Yes. Yes Okay, so you need the mini gap in the proximity proximitized Normal metal so our mini gap is in the also. Sorry. Can you Repeat for the online people As I was asking how the energy which is released is Delta you yes compares to the mini gap in the Okay. Yes. So the mini gap actually we can kind of see it here as this convolution integral Shows us that you know, we have basically Delta one plus mini gap minus mini gap here You get two coherence peaks So it's in the order of several tons of micro electron volts as mini gap But the dissipation as I was saying is quite violent. It's in the mille-electron range So we are dissipate we are actually depositing something around 10 to 15 even more Millie-electron volts to the end. So it's just that Basically shooting the temperature to 200 a mili Kelvin. So, yes I talked about this relaxing part and then as the final cure what we this is just the to say that actually Everything is in line with our calculations. We are basically taking the Delta T for every temperature and then try We fit it with our calculations based on the heat capacity of our normal metal and as I just mentioned the the energy that we are depositing on On the end, but there is a catch actually as it's a round-trip facelift So we are actually measuring two facelifts, but the the way back The second facelift as it starts from it from a higher temperature Actually, it's depositing less energy and this is basically to show that we take this into account and what we find in the end is In line with our experimental observations So, yeah to sum up things So although we are not pushing the the limits the frontiers of let's say Metric detection this can be seen as in my opinion as an interesting Demonstration of real-time thermometry for something interesting scientific wise and There can be yeah, we actually wanted to also probe the The phase dependence of the heat capacity of n as it's an approximatized Metal it should in principle be dependent on the phase we impose but Given our Experimental temperature it was not possible to observe such phenomenon that I would like to thank you for your attention and some questions You are Very interesting. I'm wondering Have you performed a control experiment where this where you don't allow the facelift to happen? Yes, and yeah, and do you see any dissipation that yes so I would like to maybe so this is our experimental setup and So this Flux this flux line that we use to pro generate the facelift is actually not impedance matched To the flux to the to the circuit. So which means that at every temperature we first need to go and prickly Increase the voltage amplitude the pulse amplitude until we observe that the the phases happening So this is basically that We are basically increasing the pulse amplitude, but it's a it's a very Longer pulse, but these blue curves shows that Actually, these are just responses to the phase bias that we impose There's no dissipation going on but there is a threshold value beyond which if you Exceed this threshold value then What you observe next is just the term of relaxation Because in the in between Your phase is basically fixed by the up Signal of your pulse. So there's no phase change in that in between It's interesting, but it's not obvious to me why the red line is where the red plateau is below the blue ones, right? I mean, why why is there? Why is the non-dissipative response less For the red line? I'm sorry. Do I'm not sure if I understood correctly So so I understand the red line the difference between the red line and the blue shades Yes, is that it has a peak. Yes, that's one difference. So there is also a relaxing part Yes, but but it relaxes to lower than the blue ones and that's confusing to me It should relax if there blue is the background simply put if blue is background, why isn't red relaxing to blue? Yeah, exactly so Maybe it's too technical. Maybe it's a detail That this can be also so the question is why he's not going back to To the base line Okay, so there can be some background heating that maybe we need to take into account Wait below the other ones. Okay, so maybe if we so okay so imagine Now you want to know what's the amplitude that generates a facelift So you basically increase the amplitude of your pulse So first one is doing that the second one is doing this that and that and then in the end your last one is just basically Exceeding the threshold and you're landing here Yes, okay Maybe we should discuss that during the break. I think Mikko you had a question I think you need to ask the microphone so online people I was just interesting at what is the material of the normal medallus? Sorry. I missed that copper copper. Yeah And in this delta T you saw that the delta T kind of goes down exponentially when you increase the temperature But still to me if I look at the you know at the peaks at the highest temperature that you get for each of those Peaks on on the on the left plot. They were like they were going up when you increase the temperature. So my question is that When you increase the temperature, could it be possible that actually the peak on the left that would be lower at higher temperature Or is that already the case? It's got a little bit difficult to see there Is that the case? Relative to the background it gets lower, but the absolute value of the peak at least to me that seems that Yellow one is the highest at the peak. Okay. So actually maybe this can help So basically Actually, we there's also we also observed double jumps that I couldn't mention but here What we see is that the initial beta and the beta that we get after the jump and as screening parameter is temperature dependent basically, it's just the temperature the dependence of the critical current and what we see is that actually it's For low temperatures kind of Corresponding to a how to say to a saturation, but as you Go to the higher temperatures Yeah, I mean there's there's It's it's hard to have to say it's hard to give It's hard to give a direct answer because you need to again Put in your calculations the dissipation that is coming from the jump your initial temperature the heat capacity at that Temperature and then get the delta T so I cannot say that it increases linearly Okay, thank you. I'm sorry. I think we have to stay on time and thanks if you again