Measuring cotunneling in its wake

Zilberberg, Oded; Carmi, Assaf; Romito, Alessandro

doi:10.1103/physrevb.90.205413

Cited by 21 publications

(34 citation statements)

References 42 publications

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“…Much effort has gone into the microscopic understanding of the measurement process and its interrelation with backaction, treating quantum averaged evolutions [11][12][13][14][15][16], selective system dynamics [17,18], and correlated weak-strong measurements in the form of weak values [19][20][21][22][23][24]. Quantum dots in transport [11,12,[24][25][26], isolated double quantum dots [15][16][17][18]20,21], and quantum point contacts [27][28][29][30] have played a central role in analyzing quantum measurement within the realm of mesoscopic physics.…”

Section: Introductionmentioning

confidence: 99%

Projective versus weak measurement of charge in a mesoscopic conductor

et al. 2014

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We study the charge dynamics of a quantum dot as measured by a nearby quantum point contact probing the dot via individual single-particle wave packets. We contrast the two limiting cases of weak and strong system--detector coupling exerting vanishing and strong back-action on the system and analyze the resulting differences in the charge-charge correlator. Extending the study to multiple projective measurements modelling a continuous strong measurement, we identify a transition from a charge dynamics dominated by the system's properties to a universal dynamics governed by the measurement

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Section: Introductionmentioning

confidence: 99%

Projective versus weak measurement of charge in a mesoscopic conductor

et al. 2014

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“…We note that the S shape approaches a straight line upon reducing sensor bias. Thus, this is a sensor backaction effect [44] not included in the model. We emphasize that only this S shape is a backaction effect-the exchange process itself is present in absence of charge sensing.…”

Section: Prl 115 106804 (2015) P H Y S I C a L R E V I E W L E T T Ementioning

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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“…However, this estimate underestimates the broadening observed in the experiment. Further, this process should conserve the area under the current peak in the system dot 14 , which is not observed experimentally. This type of level broadening is therefore insufficient to explain the observed experimental data, indicating that processes similar to Fig.…”

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confidence: 99%

“…Back-action of the detector on the system can lead to a spectral broadening of the dot energy levels as well as to detectorassisted transport. 14 The observation of those higher order effects is difficult as it is only possible if competing processes such as broadening by temperature or tunneling are sufficiently reduced.…”

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confidence: 99%

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Measurement Back-Action in Stacked Graphene Quantum Dots

et al. 2015

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We present an electronic transport experiment in graphene where both classical and quantum mechanical charge detector back-action on a quantum dot are investigated. The device consists of two stacked graphene quantum dots separated by a thin layer of boron nitride. This device is fabricated by van der Waals stacking and is equipped with separate source and drain contacts to both dots. By applying a finite bias to one quantum dot, a current is induced in the other unbiased dot. We present an explanation of the observed measurement-induced current based on strong capacitive coupling and energy dependent tunneling barriers, breaking the spatial symmetry in the unbiased system. This is a special feature of graphene-based quantum devices. The experimental observation of transport in classically forbidden regimes is understood by considering higher order quantum mechanical back-action mechanisms.

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Measuring cotunneling in its wake

Cited by 21 publications

References 42 publications

Projective versus weak measurement of charge in a mesoscopic conductor

Projective versus weak measurement of charge in a mesoscopic conductor

Intrinsic Metastabilities in the Charge Configuration of a Double Quantum Dot

Measurement Back-Action in Stacked Graphene Quantum Dots

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