
quEEGNet: Quantum AI for Biosignal Processing
Toshiaki Koike-Akino, Ye Wang
Mitsubishi Electric Research Laboratories (MERL)
201 Broadway, Cambridge, MA 02139, USA
{koike, yewang}@merl.com
Abstract—In this paper, we introduce an emerging quantum
machine learning (QML) framework to assist classical deep
learning methods for biosignal processing applications. Specif-
ically, we propose a hybrid quantum-classical neural network
model that integrates a variational quantum circuit (VQC)
into a deep neural network (DNN) for electroencephalogram
(EEG), electromyogram (EMG), and electrocorticogram (ECoG)
analysis. We demonstrate that the proposed quantum neural
network (QNN) achieves state-of-the-art performance while the
number of trainable parameters is kept small for VQC.
Index Terms—Quantum computing, deep neural network
(DNN), quantum machine learning (QML), electroencephalo-
gram (EEG), electromyogram (EMG), biosignal processing
I. INTRODUCTION
The great advancement of artificial intelligence (AI) tech-
niques based on deep neural networks (DNN) has enabled
practical development of human-machine interfaces (HMI)
including brain-computer interfaces (BCI) through the analysis
of the user’s physiological data [1], such as electroencephalo-
gram (EEG) [2] and electromyogram (EMG) [3]. However,
such biosignals are highly prone to variation depending on
the biological states of each subject [4]. Hence, frequent
calibration is often required in typical HMI systems. Toward
resolving this issue, subject-invariant methods [5]–[11], em-
ploying domain generalization and transfer learning, have been
proposed to reduce user calibration for HMI systems.
In this paper, we introduce an emerging framework “quan-
tum machine learning (QML)” [12]–[31] into biosignal pro-
cessing applications for the first time in the literature, envision-
ing future era of quantum supremacy [32], [33]. Quantum com-
puters have the potential to realize computationally efficient
signal processing compared to traditional digital computers
by exploiting quantum mechanisms, e.g., superposition and
entanglement, in terms of not only execution time but also
energy consumption. In the past few years, several vendors
have successfully manufactured commercial quantum process-
ing units (QPUs). For instance, IBM released 127-qubit QPUs
in 2021, and plans to produce 1121-qubit QPUs by 2023.
It is thus no longer far future when QML will be widely
used for real applications. Recently, hybrid quantum-classical
algorithms based on the variational principle [34]–[37] were
proposed to deal with quantum noise.
The main contributions of this paper are summarized below:
•We introduce the emerging QML framework for biosignal
processing;
•We propose a hybrid quantum-classic DNN model called
quEEGNet;
•We demonstrate the proof-of-concept study on QML for
various physiological datasets.
To the best of our knowledge, this is the very first research on
QML applied to HMI and BCI fields. Although there exist
a few literature [38], [39] discussing the potential use of
quantum computing for BCI, no practical demonstration on
QML-assisted HMI systems is found to date. Note that our
QNN is different from a recurrent QNN (RQNN) employing
quantum stochastic filtering based on the Schr¨
odinger equa-
tion [40]–[43], which is motivated by quantum physics but
does not need real QPUs. In addition, our work is tangential
to quantum sensing technologies such as superconducting
quantum interference devices (SQUID) [44].
II. QUANTUM ARTIFICIAL INTELLIGENCE (QAI) FOR HMI
A. Quantum Bit (Qubit)
In quantum systems, a qubit is expressed as the following
state superposing bases of |0iand |1i:|φi=α0|0i+α1|1i,
where α1and α2are complex numbers subject to |α0|2+
|α1|2= 1. When qubits are measured, the classical bit 0or 1is
observed with a probability of |α0|2or |α1|2, respectively. The
above ket-notation corresponds to column-vector operations of
the two basis states |0i= [1,0]Tand |1i= [0,1]T, whereas
the bra-notation is used for row-vector operations corresponds
to its Hermitian transpose; i.e., hφ|=|φi†= [α∗
0, α∗
1].
Here, [·]†,[·]∗and [·]Tdenote Hermitian transpose, complex
conjugate and transpose, respectively. Note that a multi-qubit
state is represented by sum of Kronecker products of basis
vectors such as |000i=|0i⊗3.
B. Quantum Gates
The basic operations on a qubit is defined as a unitary
matrix, which is called gate. Some of the most common gates
are associated with Pauli matrices: I= [ 1 0
0 1 ],X= [ 0 1
1 0 ],
Y=0−
0, and Z=1 0
0−1, where is the imaginary unit
satisfying 2=−1. The X gate is bit-flip (i.e., NOT operation),
Z gate is phase-flip, and Y gate flips both bit and phase. The
Hadamard (H) gate is used to generate a superposition state
|+i=1
√2|0i+1
√2|1i:H=1
√21 1
1−1. A controlled-NOT
(CNOT or CX) gate is a multi-qubit gate that flips the target
qubit if and only if the control qubit is |1i.
C. Quantum Machine Learning (QML)
A number of modern DNN methods have been already
migrated into the quantum domain, e.g., convolutional lay-
ers [12], autoencoders [13], graph neural networks [17], and
arXiv:2210.00864v1 [quant-ph] 29 Sep 2022