Method for cooling nanostructures to microkelvin temperatures

Clark, Anthony C.; Schwarzwälder, Kai Kurt; Bandi, Tobias; Maradan, Dario; Zumbühl, Dominik M.

doi:10.1063/1.3489892

Cited by 36 publications

(40 citation statements)

References 23 publications

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“…To account for these challenges special care was taken on damping all connections to the fridge and decoupling the PT cold head 21 from the rest of the system. The presented setup was improved from a previous wet system 6,7 to particularly meet the demands of a cryogen-free system 21 . We introduced a rigid support structure and an adapted geometry of the NRs.…”

Section: Nuclear Refrigerator Network Onmentioning

confidence: 99%

“…To investigate such phenomena, one needs to access lower temperatures beyond what a dilution refrigerator could achieve. Adiabatic Nuclear Demagnetization (AND) 5,6 is a well very well established technique with the potential to open the door to the µK-regime for nanoelectronics. In many laboratories, the sample is only weakly coupled to the coldest spot of the refrigerator, resulting in sample temperatures significantly higher than the base temperature of the refrigerator.…”

Section: Introductionmentioning

confidence: 99%

“…In many laboratories, the sample is only weakly coupled to the coldest spot of the refrigerator, resulting in sample temperatures significantly higher than the base temperature of the refrigerator. In order to efficiently couple sample and refrigerator, a parallel network of Nuclear Refrigerators (NRs) was proposed 6,7 , where every lead is well thermalized through the mixing chamber (MC) and has its own NR. Our approach relies on the Wiedemann-Franz cooling of the conduction electrons 8 , which is the main cooling mechanism in the mK-regime and below.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic cooling for microkelvin nanoelectronics on a cryofree platform

Palma

Maradan

Casparis

et al. 2017

Review of Scientific Instruments

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We present a parallel network of 16 demagnetization refrigerators mounted on a cryofree dilution refrigerator aimed to cool nanoelectronic devices to sub-millikelvin temperatures. To measure the refrigerator temperature, the thermal motion of electrons in a Ag wirethermalized by a spot-weld to one of the Cu nuclear refrigerators -is inductively picked-up by a superconducting gradiometer and amplified by a SQUID mounted at 4 K. The noise thermometer as well as other thermometers are used to characterize the performance of the system, finding magnetic field independent heat-leaks of a few nW/mol, cold times of several days below 1 mK, and a lowest temperature of 150 µK of one of the nuclear stages in a final field of 80 mT, close to the intrinsic SQUID noise of about 100 µK. A simple thermal model of the system capturing the nuclear refrigerator, heat leaks, as well as thermal and Korringa links describes the main features very well, including rather high refrigerator efficiencies typically above 80 %.

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Section: Nuclear Refrigerator Network Onmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetic cooling for microkelvin nanoelectronics on a cryofree platform

Palma

Maradan

Casparis

et al. 2017

Review of Scientific Instruments

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“…The experiment was done in a dilution refrigerator at base temperature T ∼ 20 mK. Ag-epoxy microwave filters and thermalizers [23] are mounted at the mixing chamber for improved cooling [24,25], giving an electron temperature of T e ∼ 60 mK from Coulomb blockade thermometry [26]. All data presented here were acquired with the left sensor dot, though the right sensor gives essentially the same results.…”

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confidence: 99%

Intrinsic Metastabilities in the Charge Configuration of a Double Quantum Dot

et al. 2015

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We report a thermally activated metastability in a GaAs double quantum dot exhibiting real-time charge switching in diamond shaped regions of the charge stability diagram. Accidental charge traps and sensor backaction are excluded as the origin of the switching. We present an extension of the canonical double dot theory based on an intrinsic, thermal electron exchange process through the reservoirs, giving excellent agreement with the experiment. The electron spin is randomized by the exchange process, thus facilitating fast, gate-controlled spin initialization. At the same time, this process sets an intrinsic upper limit to the spin relaxation time. DOI: 10.1103/PhysRevLett.115.106804 PACS numbers: 73.21.La, 73.23.Hk, 73.63.Kv Spins in quantum dots [1] are promising candidates for the realization of qubits-the elementary units of a quantum computer. Great progress was made in recent years towards implementing quantum information processing schemes with electron spins in GaAs quantum dots [2][3][4][5][6][7][8], which hold the potential for scaling to a large number of qubits [9][10][11]. Stable qubits with long coherence times are of crucial importance to execute numerous coherent quantum gates. Spin echo and dynamical decoupling techniques were successfully employed to isolate the electronic system from the slowly fluctuating nuclear spins of the GaAs host material [3,[12][13][14][15], enhancing the coherence time T 2 from below 1 μs to much longer times exceeding 0.2 ms. A fundamental limit T 2 ≤ 2T 1 is set by the spin relaxation time T 1 . In a magnetic field, spins relax through spin-phonon coupling mediated by the spin-orbit interaction [2,[16][17][18]. Since here the spin-orbit coupling is weak, very long T 1 times result, exceeding 1 s at 1 T [19], leaving ample room for further improvements of the spin qubit coherence.In this Letter, we report the experimental observation of a thermal electron exchange process via the reservoirs of a quantum dot, setting an intrinsic upper bound to T 1 , which can be orders of magnitude lower than the fundamental spin-phonon limit [16]. The resulting metastable charge states-appearing in the double dot (DD) in the absence of interdot tunneling-make the exchange process detectable with a charge sensor. Within a diamond shaped region, the DD switches its charge state back and forth over time from an electron on the left dot to an electron on the right dot without direct interdot tunneling. After excluding unintentional charge traps and sensor backaction, we present an extension of the orthodox DD transport theory accounting very well for the observations. The exchange process can be used for fast qubit initialization [7]. Finally, we outline ways to extend T 1 up to the spin-phonon limit.The sample is fabricated from a GaAs heterostructure with a 2D electron gas 110 nm below the surface (density 2.6 × 10 11 cm −2 and mobility 4 × 10 5 cm 2 =V s). The device layout, see Fig. 1(a), is adopted from Ref. [20]. Each dot adjacent to the DD (center) acts as a charge sensor [...

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“…Nongalvanic thermometry for ultracold two-dimensional electron domains S. Gasparinetti, 1,a) M. J. Martínez-Pé rez, 2 S. de Franceschi, 3 J. P. Pekola, 1 Measuring the temperature of a two-dimensional electron gas at temperatures of a few mK is a challenging issue, which standard thermometry schemes may fail to tackle. We propose and analyze a nongalvanic thermometer, based on a quantum point contact and quantum dot, which delivers virtually no power to the electron system to be measured.…”

mentioning

confidence: 99%