Charge sensing of a few-donor double quantum dot in silicon

Abstract

We demonstrate the charge sensing of a few-donor double quantum dot precision placed with atomic resolution scanning tunnelling microscope lithography. We show that a tunnel-coupled single electron transistor (SET) can be used to detect electron transitions on both dots as well as inter-dot transitions. We demonstrate that we can control the tunnel times of the second dot to the SET island by ∼4 orders of magnitude by detuning its energy with respect to the first dot.

Extracting inter-dot tunnel couplings between few donor quantum dots in silicon

“…Nanoelectronic devices based on phosphorus doped silicon (Si:P) have recently demonstrated electron transport at the few electron level where spin-spin interactions can be observed [12][13][14]. Following this, the singlet-triplet states of a strongly coupled donor pair have been readout [15] and electrons confined to double QDs formed from donor clusters have been investigated using charge-sensing [16]. Importantly, for the scalability of multi-donor systems in a quantum computing architecture, the ability to simply and reliably measure t c between donors is vital.…”

Mapping the chemical potential landscape of a triple quantum dot

“…As the complexity of coupled QD devices increases so does the electronic tunneling processes that occur within them [5][6][7]. In particular, for multi-QD systems, the tunneling of electrons from dot to dot will often occur in multiple stages resulting in nontrivial tunneling paths.…”

High-Fidelity Single-Shot Singlet-Triplet Readout of Precision-Placed Donors in Silicon

“…Unlike in gate-defined quantum dots, donor systems do not require electrodes to confine electrons. The resulting decrease in physical complexity makes donor nanodevices very appealing for scaling up to many electron sites [15].In the (1,1) charge configuration the ST states are eigenstates if the exchange coupling is greater than any difference in Zeeman energy between the two spins. The singlet and three triplet states are split only by the Zeeman energy in the cases of jT þ i ¼ j↑↑i and jT − i ¼ j↓↓i, and an exchange energy, J, for the singlet jSi ¼ ðj↑↓i − j↓↑iÞ= ffiffi ffi 2 p and jT 0 i ¼ ðj↑↓i þ j↓↑iÞ= ffiffi ffi 2 p states.…”

“…The spin of a single electron in the solid state has long been utilized in this context [5][6][7][8][9][10][11], providing a superbly clean quantum system with two orthogonal quantum states that can be measured with over 99% fidelity [12]. As a natural next step, the coupling of two electrons at separate sites has been studied in gate-defined quantum dots [5,13,14], as well as in donor systems [15][16][17]. In addition to being the eigenstates for two coupled spins, the singlet-triplet (ST) states of two electrons can form a qubit subspace, and have previously been utilized for quantum information processing [6,[18][19][20][21][22].…”

“…Unlike in gate-defined quantum dots, donor systems do not require electrodes to confine electrons. The resulting decrease in physical complexity makes donor nanodevices very appealing for scaling up to many electron sites [15].…”