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arXiv:2604.00138

Quantum memory on a nanophotonic silicon chip

Stephan Rinner, Jonas Schmitt, Kilian Sandholzer, Andreas Reiserer

quant-phcond-mat.otherSubmitted Mar 31, 2026• Announced Apr 2, 2026• 1 citation
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Abstract

Integrated photonic circuits offer great promise for quantum technologies. However, due to the rapid propagation of light, many envisioned applications require efficient on-chip quantum memories with a programmable delay, compact footprint, and high fidelity. Implementing this based on standard semiconductor processing technology is an outstanding challenge. Here, we realize such memories using erbium-doped silicon waveguides, fabricated as part of a multi-wafer project by a nanophotonic foundry. We demonstrate light storage with a $44.2(9)\ \text{MHz}$ bandwidth and a programmable delay exceeding $1\ μ\text{s}$ in a device with a footprint of only $1.5\times 10^{-2}\ \text{mm}^2$, outperforming on-chip delay lines by many orders of magnitude. The phase of the read-out light field is preserved with a visibility of $91.3(30)\ \%$. The efficiency of $1.89(28)\times 10^{-8}$ can be improved in future devices through resonator enhancement and higher dopant concentrations. With this, the demonstrated approach will pave the way towards applications in photonic quantum computing based on scalable silicon processing technology.

Comments
11 pages, 4 figures

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Integrated photonic circuits offer great promise for quantum technologies. However, due to the rapid propagation of light, many envisioned applications require efficient on-chip quantum memories with a programmable delay, compact footprint, and high fidelity. Implementing this based on standard semiconductor processing technology is an outstanding challenge. Here, we realize such memories using erbium-doped silicon waveguides, fabricated as part of a multi-wafer project by a nanophotonic foundry. We demonstrate light storage with a 44.2(9) MHz44.2(9)\ \text{MHz}44.2(9) MHz bandwidth and a programmable delay exceeding 1 μs1\ μ\text{s}1 μs in a device with a footprint of only 1.5×10−2 mm21.5\times 10^{-2}\ \text{mm}^21.5×10−2 mm2, outperforming on-chip delay lines by many orders of magnitude. The phase of the read-out light field is preserved with a visibility of 91.3(30) %91.3(30)\ \%91.3(30) %. The efficiency of 1.89(28)×10−81.89(28)\times 10^{-8}1.89(28)×10−8 can be improved in future devices through resonator enhancement and higher dopant concentrations. With this, the demonstrated approach will pave the way towards applications in photonic quantum computing based on scalable silicon processing technology.
Quantum memories integrated into nanophotonic silicon devices are a promising platform for large quantum networks and scalable photonic quantum computers. In this context, erbium dopants are particularly attractive, as they combine optical transitions in the telecommunications frequency band with the potential for second-long coherence time. Here, we show that these emitters can be reliably integrated into commercially fabricated low-loss waveguides. We investigate several integration procedures and obtain ensembles of many emitters with an inhomogeneous broadening of <2 GHz and a homogeneous linewidth of <30 kHz. We further observe the splitting of the electronic spin states in a magnetic field up to 9 T that freezes paramagnetic impurities. Our findings are an important step toward long-lived quantum memories that can be fabricated on a wafer-scale using CMOS technology.
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Quantum-based communication systems can potentially achieve the ultimate security from eavesdropping and greatly reduce the operating powers on chip. Light-speed transmission, noise immunity, and low noise properties make photons indispensable for quantum communication to transfer a quantum state through a transmission line. Furthermore, the field of silicon nanophotonics is fast growing field which is driven by the attractive and promising improvements it has to offer in high speed communication systems and on chip optical interconnects. Consequently, there is a high demand to develop the building blocks for photon manipulation in silicon nanophotonic circuits. The goal of the work is to enable high performance optoelectronic computing and communication systems that overcome the barriers of electronics and dramatically enhance the performance of circuits and systems. We will focus our attention on solving some of the issues with the current systems regarding photon storage, routing, isolation, switching, and energy conversion. We realize a continuously tunable optical memory which breaks the time-bandwidth limit by more than thirty times. This enabled the storage of ultra-short pulses of light for hundreds of picoseconds. Also, we investigate on-chip photon scattering when transmitted through micro-scale optical cavities. In addition, we develop novel dynamic quantum mechanical models that predict quantum-like behavior of single and multi-photon wavepackets. Furthermore, we report for the first time that efficient red shifts in silicon are achievable with free carrier injection which generally produces blue wavelength shifts. We realize adiabatic wavelength conversion and discrete photonic transitions of single photons in silicon cavities. Moreover, we demonstrate a basic quantum network on chip with an on-chip photon source. We present a novel design for CMOS compatible optical isolator on silicon chip using a system of active cavities. And finally, we analyze a novel ultra-fast broadband modulator in silicon based on free-carrier absorption effect in SOI waveguides integrated with Schottky diodes.
Quantum memories for light are essential building blocks for quantum repeaters and quantum networks. Integrated operations of quantum memories could enable scalable application with low-power consumption. However, the photonic quantum storage lifetime in integrated devices has so far been limited to tens of microseconds, falling short of the requirements for practical applications. Here, we demonstrate quantum storage of photonic qubits for 1.021 milliseconds based on a laser-written optical waveguide fabricated in a 151 Eu 3+ :Y 2 SiO 5 crystal. Spin dephasing of 151 Eu 3+ is mitigated through dynamical decoupling applied via on-chip electric waveguides, and we obtain a storage efficiency of 12.0 ± 0.5% at 1.021 milliseconds, which is a demonstration of integrated quantum memories that outperforms the efficiency of a simple fiber delay line. Such long-lived waveguide-based quantum memory could support applications in quantum repeaters, and further combination with critical magnetic fields could enable potential application as transportable quantum memories.
Storing and retrieving photonic qubits are key functionalities in future optical quantum networks, and integrating scalable optical-memory units is crucial as these networks expand. However, attempts to combine silicon photonics and erbium ions for telecom memories, without losing the scalable and low-loss properties of silicon chips, face challenges because of limited light-matter interactions and potential extra decoherence. Here, we present an efficient silicon-chip platform using bound states in the continuum to overcome these limitations. In addition to a low propagation loss of 0.5 ± 0.5 decibels per centimeter, our experiments demonstrate an order-of-magnitude enhancement in light absorption compared to previous traditional silicon hybrid designs. Using these properties, we demonstrated photon echoes in our waveguide structures, revealing a coherence time of 2.6 ± 0.6 microseconds at zero magnetic field, closely matching that of bulk crystals. These characteristics make the bound state in the continuum platform a promising candidate for realizing integrated optical memories for quantum network applications.
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